Endothelin-1-induced bronchoconstriction in asthma

Saffron (Crocus sativus) and its constituents in ovalbumin-induced asthma model: a preclinical systematic review and meta-analysis

Background

Animal and human studies have demonstrated that the saffron and the active components of saffron, including crocin, crocetin, and safranal, possess anti-inflammatory, antioxidant, and immunomodulatory properties. In this meta-analysis, the preclinical evidence and potential mechanism of saffron were explored in an animal model of ovalbumin-induced asthma.

Methods

Studies related to saffron and its constituents in an animal model of ovalbumin-induced asthma from the beginning to March 2024 were searched from Scopus, PubMed, and Web of Science databases. The methodological quality of the studies was evaluated using the 15-item CAMARADES checklist. Data analysis was performed using STATA software version 17.

Results

Thirteen studies with 536 animals (268 animals in the intervention group and 268 animals in the ovalbumin-induced group) were analyzed. The meta-analysis findings demonstrated that saffron and its constituents played a significant role in reducing total WBC, eosinophil, lymphocyte, and monocyte counts. Moreover, saffron showed a significant decrease in the levels of IL-4, IL-5, IL-13, IgE, histamine, endothelin, nitric oxide, and nitrite. Moreover, saffron was found to elevate EC50 thresholds and lower maximum response rates in experimental animals. The analysis revealed a significant identification of modulation in endoplasmic reticulum (ER) stress markers and miRNAs pathways.

Conclusion

Saffron and its components may impact ovalbumin-induced asthma model in animals through anti-inflammatory, antioxidant, and immunomodulatory pathways, as well as improving pulmonary function and modulating ER stress markers and miRNAs pathways. As a result, saffron should be considered for further clinical trials in individuals suffering from asthma.

Rhinovirus infection induces secretion of endothelin-1 from airway epithelial cells in both in vitro and in vivo models

BACKGROUND

Rhinovirus (RV) infection of airway epithelial cells triggers asthma exacerbations, during which airway smooth muscle (ASM) excessively contracts. Due to ASM contraction, airway epithelial cells become mechanically compressed. We previously reported that compressed human bronchial epithelial (HBE) cells are a source of endothelin-1 (ET-1) that causes ASM contraction. Here, we hypothesized that epithelial sensing of RV by TLR3 and epithelial compression induce ET-1 secretion through a TGF-β receptor (TGFβR)-dependent mechanism.

METHODS

To test this, we used primary HBE cells well-differentiated in air-liquid interface culture and two mouse models (ovalbumin and house dust mite) of allergic airway disease (AAD). HBE cells were infected with RV-A16, treated with a TLR3 agonist (poly(I:C)), or exposed to compression. Thereafter, EDN1 (ET-1 protein-encoding gene) mRNA expression and secreted ET-1 protein were measured. We examined the role of TGFβR in ET-1 secretion using either a pharmacologic inhibitor of TGFβR or recombinant TGF-β1 protein. In the AAD mouse models, allergen-sensitized and allergen-challenged mice were subsequently infected with RV. We then measured ET-1 in bronchoalveolar lavage fluid (BALF) and airway hyperresponsiveness (AHR) following methacholine challenge.

RESULTS

Our data reveal that RV infection induced EDN1 expression and ET-1 secretion in HBE cells, potentially mediated by TLR3. TGFβR activation was partially required for ET-1 secretion, which was induced by RV, poly(I:C), or compression. TGFβR activation alone was sufficient to increase ET-1 secretion. In AAD mouse models, RV induced ET-1 secretion in BALF, which positively correlated with AHR.

CONCLUSIONS

Our data provide evidence that RV infection increased epithelial-cell ET-1 secretion through a TGFβR-dependent mechanism, which contributes to bronchoconstriction during RV-induced asthma exacerbations.

Endothelin-1 in Health and Disease

Discovered almost 40 years ago, the potent vasoconstrictor peptide endothelin-1 (ET-1) has a wide range of roles both physiologically and pathologically. In recent years, there has been a focus on the contribution of ET-1 to disease. This has led to the development of various ET receptor antagonists, some of which are approved for the treatment of pulmonary arterial hypertension, while clinical trials for other diseases have been numerous yet, for the most part, unsuccessful. However, given the vast physiological impact of ET-1, it is both surprising and disappointing that therapeutics targeting the ET-1 pathway remain limited. Strategies aimed at the pathways influencing the synthesis and release of ET-1 could provide new therapeutic avenues, yet research using cultured cells in vitro has had little follow up in intact ex vivo and in vivo preparations. This article summarises what is currently known about the synthesis, storage and release of ET-1 as well as the role of ET-1 in several diseases including cardiovascular diseases, COVID-19 and chronic pain. Unravelling the ET-1 pathway and identifying therapeutic targets has the potential to treat many diseases whether through disease prevention, slowing disease progression or reversing pathology.

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.

Endothelin A (ETA) and Endothelin B (ETB) Receptor Subtypes Potentiate Epidermal Growth Factor (EGF)-Mediated Proliferation in Human Asthmatic Bronchial Airway Smooth Muscle

Background

Asthma is a chronic disease characterized by chronic inflammation, reversible airway obstruction, airway hyperresponsiveness (AHR), and airway remodeling. One of the important features of asthma is airway remodeling, which plays a central role in airflow limitation. Airway remodeling involves numerous changes in the bronchial walls, including airway smooth muscle (ASM) cell hypertrophy and hyperplasia. Studies have shown that ASM hyperplasia in asthma is mediated by the increased production of mitogens. Endothelin-1 (ET-1) has been shown to induce proliferation and function as a co-mitogen in vascular and ASM. In patients with asthma, plasma and bronchoalveolar lavage fluid have been shown to have elevated ET-1 levels, which have been linked to airway remodeling and airflow obstruction in severe asthma. This study investigates the role of ET-1 in proliferation, the receptor subtype mediating its effect, and the signaling pathway.

Methodology

Normal and asthmatic bronchial airway smooth muscle (BASM) cells were seeded into 5 × 10³ cells/well. Cell proliferation was assayed using 5-bromo-2’-deoxyuridine (BrdU) incorporation. Confluent cells were treated with different concentrations of ET-1 in the presence or absence of the epidermal growth factor (EGF). Signaling pathways were explored using pretreatment of BASM with antagonists 15 minutes before ET-1/EGF stimulation.

Results

In asthmatic BASM, ET-1 (0.1 nM) functions as a co-mitogen in the presence of EGF (10 nM), showing a significantly greater effect on asthmatic BASM proliferation compared with normal BASM. The ETA receptor antagonist BQ-123 (10-1,000 nM) significantly reduced the proliferative effect of ET-1/EGF on asthmatic BASM more than normal BASM. Moreover, the effect of ETB antagonist BQ-788 (1,000 nM) or pretreatment with the ETB agonist S6C (1-10 nM) followed by co-treatment with EGF in asthmatic BASM showed a small but significant decrease when pretreated with the inhibitor and increased with the agonist, thereby suggesting that the co-mitogenic effect of ET-1 is mainly via the activation of ETA receptors, with a small contribution by the ETB receptors in asthmatic BASM. Finally, pertussis toxin (PTX) pretreatment (25 and 50 ng/mL) showed that EGF and ET-1/EGF mitogenic and co-mitogenic signaling utilizes Gi/0-mediated transactivation by EGF and ET receptors, especially in asthmatic BASM, leading to the activation of Ras-ERK-PI3K pathways. Enhanced ERK and PI3K effects on proliferation suggested that these kinases modulate the co-mitogenic effect of ET-1 in asthmatic BASM. Enhanced cross-talk between ET and EGF receptors may be a potential mechanism contributing to airway remodeling in asthmatic BASM.

Conclusions

ET-1 enhances the mitogenic effect of EGF predominantly via the ETA receptor in asthmatic BASM with the activation of Ras, ERK, and PI3K. The cross-talk mechanism between ET and EGF receptors may be a potential therapeutic target to prevent the progression of airway remodeling in ASM in patients with asthma.

Imprinting of bronchial epithelial cells upon in vivo rhinovirus infection in people with asthma

Background

Defective translocation of the translational repressor TIAR (T-cell internal antigen receptor) in bronchial epithelial cells (BECs) from asthma patients underlies epithelial hyperresponsiveness, reflected by an exaggerated production of a select panel of inflammatory cytokines such as CXCL-8, interleukin (IL)-6, granulocyte colony-stimulating factor, CXCL-10, upon exposure to tumour necrosis factor (TNF) and IL-17A. With this study we aimed to clarify whether epithelial hyperresponsiveness is a consistent finding, is changed upon in vivo exposure to rhinovirus (RV)-A16 and applies to the bronchoconstrictor endothelin-1.

Methods

BECs were obtained from asthma patients (n=18) and healthy individuals (n=11), 1 day before and 6 days post-RV-A16 exposure. BECs were cultured and stimulated with TNF and IL-17A and inflammatory mediators were analysed. The bronchoalveolar lavage fluid (BALF) was obtained in parallel with BECs to correlate differential cell counts and inflammatory mediators with epithelial hyperresponsiveness.

Results

Epithelial hyperresponsiveness was confirmed in sequential samples and even increased in BECs from asthma patients after RV-A16 exposure, but not in BECs from healthy individuals. Endothelin-1 tended to increase in BECs from asthma patients collected after RV-A16 exposure, but not in BECs from healthy individuals. In vitro CXCL-8 and endothelin-1 production correlated. In vivo relevance for in vitro CXCL-8 and endothelin-1 production was shown by correlations with forced expiratory volume in 1 s % predicted and CXCL-8 BALF levels.

Conclusion

Epithelial hyperresponsiveness is an intrinsic defect in BECs from asthma patients, which increases upon viral exposure, but not in BECs from healthy individuals. This epithelial hyperresponsiveness also applies to the bronchoconstrictor endothelin-1, which could be involved in airway obstruction.

Epithelial hyperresponsiveness is an intrinsic defect in bronchial epithelium from asthma patients, which increases upon rhinovirus exposure, but not in healthy individualshttps://bit.ly/3xLhjuj

Airway mechanical compression: its role in asthma pathogenesis and progression

The lung is a mechanically active organ, but uncontrolled or excessive mechanical forces disrupt normal lung function and can contribute to the development of disease. In asthma, bronchoconstriction leads to airway narrowing and airway wall buckling. A growing body of evidence suggests that pathological mechanical forces induced by airway buckling alone can perpetuate disease processes in asthma. Here, we review the data obtained from a variety of experimental models, including in vitro, ex vivo and in vivo approaches, which have been used to study the impact of mechanical forces in asthma pathogenesis. We review the evidence showing that mechanical compression alters the biological and biophysical properties of the airway epithelium, including activation of the epidermal growth factor receptor pathway, overproduction of asthma-associated mediators, goblet cell hyperplasia, and a phase transition of epithelium from a static jammed phase to a mobile unjammed phase. We also define questions regarding the impact of mechanical forces on the pathology of asthma, with a focus on known triggers of asthma exacerbations such as viral infection.

Transcriptomic analysis reveals diverse gene expression changes in airway macrophages during experimental allergic airway disease

Background: Airway macrophages (AMs) are the most abundant leukocytes in the healthy airway lumen and have a highly specialised but plastic phenotype that is governed by signals in the local microenvironment. AMs are thought to maintain immunological homeostasis in the steady state, but have also been implicated in the pathogenesis of allergic airway disease (AAD). In this study, we aimed to better understand these potentially contrasting AM functions using transcriptomic analysis. Methods: Bulk RNA sequencing was performed on AMs (CD11c + Siglec F + CD64 + CD45 + SSC hi) flow cytometry sorted from C57BL/6 mice during experimental AAD driven by repeated house dust mite inhalation (AMs HDM), compared to control AMs from non-allergic mice. Differentially expressed genes were further analysed by hierarchical clustering and biological pathway analysis. Results: AMs HDM showed increased expression of genes associated with antigen presentation, inflammatory cell recruitment and tissue repair, including several chemokine and matrix metalloproteinase genes. This was accompanied by increased expression of mitochondrial electron transport chain subunit genes and the retinoic acid biosynthetic enzyme gene Raldh2. Conversely, AMs HDM displayed decreased expression of a number of cell cycle genes, genes related to cytoskeletal functions and a subset of genes implicated in antimicrobial innate immunity, such as Tlr5, Il18 and Tnf. Differential gene expression in AMs HDM was consistent with upstream effects of the cytokines IL-4 and IFN-γ, both of which were present at increased concentrations in lung tissue after HDM treatment. Conclusions: These data highlight diverse gene expression changes in the total AM population in a clinically relevant mouse model of AAD, collectively suggestive of contributions to inflammation and tissue repair/remodelling, but with decreases in certain steady state cellular and immunological functions.

Transcriptomic analysis reveals diverse gene expression changes in airway macrophages during experimental allergic airway disease

Background: Airway macrophages (AMs) are the most abundant leukocytes in the healthy airway lumen and have a highly specialised but plastic phenotype that is governed by signals in the local microenvironment. AMs are thought to maintain immunological homeostasis in the steady state, but have also been implicated in the pathogenesis of allergic airway disease (AAD). In this study, we aimed to better understand these potentially contrasting AM functions using transcriptomic analysis. Methods: Bulk RNA sequencing was performed on AMs flow cytometry sorted from C57BL/6 mice during experimental AAD driven by repeated house dust mite inhalation (AMs HDM), compared to control AMs from non-allergic mice. Differentially expressed genes were further analysed by hierarchical clustering and biological pathway analysis. Results: AMs HDM showed increased expression of genes associated with antigen presentation, inflammatory cell recruitment and tissue repair, including several chemokine and matrix metalloproteinase genes. This was accompanied by increased expression of mitochondrial electron transport chain subunit genes and the retinoic acid biosynthetic enzyme gene Raldh2. Conversely, AMs HDM displayed decreased expression of a number of cell cycle genes, genes related to cytoskeletal functions and a subset of genes implicated in antimicrobial innate immunity, such as Tlr5, Il18 and Tnf. Differential gene expression in AMs HDM was consistent with upstream effects of the cytokines IL-4 and IFN-γ, both of which were present at increased concentrations in lung tissue after HDM treatment. Conclusions: These data highlight diverse gene expression changes in the total AM population in a clinically relevant mouse model of AAD, collectively suggestive of contributions to inflammation and tissue repair/remodelling, but with decreases in certain steady state cellular and immunological functions.

Airway epithelial compression promotes airway smooth muscle proliferation and contraction

During acute bronchoconstriction, the airway epithelium becomes mechanically compressed, as airway smooth muscle contracts and the airway narrows. This mechanical compression activates airway epithelium to promote asthmatic airway remodeling. However, whether compressed airway epithelium can feed back on the cause of bronchoconstriction has remained an open question. Here we examine the potential for epithelial compression to augment proliferation and contraction of airway smooth muscle, and thus potentiate further bronchoconstriction and epithelial compression. Well-differentiated primary human bronchial epithelial (HBE) cells maintained in air-liquid interface culture were mechanically compressed to mimic the effect of bronchoconstriction. Primary human airway smooth muscle (HASM) cells were incubated with conditioned media collected from mechanically compressed HBE cells to examine the effect of epithelial-derived mediators on HASM cell proliferation using an EdU assay and HASM cell contraction using traction microscopy. An endothelin receptor antagonist, PD-145065, was employed to probe the role of HBE cell-derived endothelin-1 on the proliferation and contraction of HASM cells. Conditioned media from compressed HBE cells increased HASM cell proliferation, independent of the endothelin-1 signaling pathway. However, conditioned media from compressed HBE cells significantly increased HASM cell basal contraction and histamine-induced contraction, both of which depended on the endothelin-1 signaling pathway. Our data demonstrate that mechanical compression of bronchial epithelial cells contributes to proliferation and basal contraction of airway smooth muscle cells and that augmented contraction depends on epithelial cell-derived endothelin-1. By means of both airway smooth muscle remodeling and contractility, our findings suggest a causal role of epithelial compression on asthma pathogenesis.

Inundation of asthma target research: Untangling asthma riddles

Asthma is an inveterate inflammatory disorder, delineated by the airway inflammation, bronchial hyperresponsiveness (BHR) and airway wall remodeling. Although, asthma is a vague term, and is recognized as heterogenous entity encompassing different phenotypes. Targeting single mediator or receptor did not prove much clinical significant, as asthma is complex disease involving myriad inflammatory mediators. Asthma may probably involve a large number of different types of molecular and cellular components interacting through complex pathophysiological pathways. This review covers the past, present, and future therapeutic approaches and pathophysiological mechanisms of asthma. Furthermore, review describe importance of targeting several mediators/modulators and receptor antagonists involved in the physiopathology of asthma. Novel targets for asthma research include Galectins, Immunological targets, K ⁺ Channels, Kinases and Transcription Factors, Toll-like receptors, Selectins and Transient receptor potential channels. But recent developments in asthma research are very promising, these include Bitter taste receptors (TAS2R) abated airway obstruction in mouse model of asthma and Calcium-sensing receptor obliterate inflammation and in bronchial hyperresponsiveness allergic asthma. All these progresses in asthma targets, and asthma phenotypes exploration are auspicious in untangling of asthma riddles.

Chronic endothelin-1 infusion causes adipocyte hyperplasia in rats

OBJECTIVE

The aim of this study was to investigate the regulatory mechanism of endothelin-1 (ET-1), an endothelium-derived vasoconstrictor, on adipogenesis in vitro and in vivo.

METHODS

3T3-L1 preadipocytes were used to explore the mechanisms mediating ET-1 actions on preadipocyte proliferation and adipocyte differentiation. To investigate the in vivo effect of ET-1, male Sprague-Dawley rats were infused with ET-1 or saline for 4 weeks via intraperitoneally implanted osmotic pumps, and the fat pad weight and adipocyte size of adipose tissues were measured.

RESULTS

ET-1 stimulated preadipocyte proliferation and increased the cell number at the mitotic clonal expansion stage of adipocyte differentiation via the endothelin A receptor (ETAR) and activation of the protein kinase C (PKC) pathway. ET-1, via ETAR, inhibited adipocyte differentiation partially through an ERK-dependent pathway. Furthermore, no significant difference in the body weight and fat pad weight was observed in either ET-1- or saline-infused rats. Compared with saline-infused rats, the adipocyte cell number was significantly increased but the adipocyte size was significantly decreased in ET-1-infused rats.

CONCLUSIONS

Chronic ET-1 infusion increased the number of small adipocytes without the change of white adipose tissue mass in rats, which were associated with ET-1-stimulated preadipocyte proliferation, but not ET-1-suppressed adipocyte differentiation.

Lung function in pulmonary hypertension

Breathlessness is a common symptom in pulmonary hypertension (PH) and an important cause of morbidity. Though this has been attributed to the well described pulmonary vascular abnormalities and subsequent cardiac remodelling, changes in the airways of these patients have also been reported and may contribute to symptoms. Our understanding of these airway abnormalities is poor with conflicting findings in many studies. The present review evaluates these studies for the major PH groups. In addition we describe the role of cardiopulmonary exercise testing in the assessment of pulmonary arterial hypertension (PAH) by evaluating cardiopulmonary interaction during exercise. As yet, the reasons for the abnormalities in lung function are unclear, but potential causes and the possible role of inflammation are discussed. Future research is required to provide a better understanding of this to help improve the management of these patients.

Chenodeoxycholic acid attenuates ovalbumin-induced airway inflammation in murine model of asthma by inhibiting the T(H)2 cytokines

Asthma is a complex highly prevalent airway disease that is a major public health problem for which current treatment options are inadequate. Recently, farnesoid X receptor (FXR) has been shown to exert anti-inflammatory actions in various disease conditions, but there have been no reported investigations of Chenodeoxycholic acid (CDCA), a natural FXR agonist, in allergic airway inflammation. To test the CDCA effectiveness in airway inflammation, ovalbumin (OVA)-induced acute murine asthma model was established. We found that lung tissue express FXR and CDCA administration reduced the severity of the murine allergic airway disease as assessed by pathological and molecular markers associated with the disease. CDCA treatment resulted in fewer infiltrations of cells into the airspace and peribronchial areas, and decreased goblet cell hyperplasia, mucus secretion and serum IgE levels which was increased in mice with OVA-induced allergic asthma. The CDCA treatment further blocked the secretion of TH2 cytokines (IL-4, IL-5 and IL-13) and proinflammatory cytokine TNF-α indicate that the FXR and its agonists may have potential for treating allergic asthma.

Epigenetics of hyper-responsiveness to allergen challenge following intrauterine growth retardation rat

Background

Epidemiological studies have revealed that intrauterine growth retardation (IUGR) or low birth weight is linked to the later development of asthma. Epigenetic regulatory mechanisms play an important role in the fetal origins of adult disease. However, little is known regarding the correlation between epigenetic regulation and the development of asthma following IUGR.

Methods

An IUGR and ovalbumin (OVA)-sensitization/challenge rat model was used to study whether epigenetic mechanisms play a role in the development of asthma following IUGR.

Results

Maternal nutrient restriction increased histone acetylation levels of the endothelin-1 (ET-1) gene promoter in lung tissue of offspring, but did not cause significant alterations of DNA methylation. The effect was maintained until 10 weeks after birth. Furthermore, these epigenetic changes may have induced IUGR individuals to be highly sensitive to OVA challenge later in life, resulting in more significant changes related to asthma.

Conclusions

These findings suggest that epigenetic mechanisms might be closely associated with the development of asthma following IUGR, providing further insight for improved prevention of asthma induced by environmental factors.

Prostaglandin E2 elicits greater bronchodilation than salbutamol in mouse intrapulmonary airways in lung slices

BACKGROUND

Current asthma therapy may not adequately target contraction of smaller intrapulmonary airways, which are a major site of airway obstruction and inflammation. The aim of this study was to characterise responses of mouse intrapulmonary airways to prostaglandin E(2) (PGE(2)) and compare its dilator efficacy with the β(2)-adrenoceptor agonist salbutamol in situ, using lung slices.

METHODS

Lung slices (150 μm) were prepared from male Balb/C mice. Changes in intrapulmonary airway lumen area were recorded and analysed by phase-contrast microscopy. Relaxation to PGE(2) and salbutamol were assessed following various levels of pre-contraction with methacholine, serotonin or endothelin-1, as well as following overnight incubation with PGE(2) or salbutamol. The mechanism of PGE(2)-mediated relaxation was explored using selective EP antagonists (EP(1/2) AH6809; EP(4) L-161982) and Ca(2+)-permeabilized slices, where airway responses are due to regulation of Ca(2+)-sensitivity alone.

RESULTS

PGE2 elicited EP(1/2)-mediated relaxation of intrapulmonary airways. PGE(2) was more potent than salbutamol in opposing submaximal pre-contraction to all constrictors tested, and only PGE(2) opposed maximal pre-contraction with endothelin-1. Relaxation to PGE(2) was maintained when contraction to methacholine was mediated via increased Ca(2+)-sensitivity alone. PGE(2) was less sensitive to homologous or heterologous desensitization of its receptors than salbutamol.

CONCLUSION

The greater efficacy and potency of PGE(2) compared to salbutamol in mouse intrapulmonary airways supports further investigation of the mechanisms underlying this improved dilator responsiveness for the treatment of severe asthma.

Environmental perturbations: Obesity

Obesity currently affects about one-third of the U.S. population, while another one-third is overweight. The importance of obesity for certain conditions such as heart disease and type 2 diabetes is well appreciated. The effects of obesity on the respiratory system have received less attention and are the subject of this article. Obesity alters the static mechanical properties of the respiratory system leading to a reduction in the functional residual capacity (FRC) and the expiratory reserve volume (ERV). There is substantial variability in the effects of obesity on FRC and ERV, at least some of which is related to the location rather than the total mass of adipose tissue. Obesity also results in airflow obstruction, which is only partially attributable to breathing at low lung volume, and can also promote airway hyperresponsiveness and asthma. Hypoxemia is common is obesity and correlates well with FRC, as well as with measures of abdominal obesity. However, obese subjects are usually eucapnic, indicating that hypoventilation is not a common cause of their hypoxemia. Instead, hypoxemia results from ventilation-perfusion mismatch caused by closure of dependent airways at FRC. Many obese subjects complain of dyspnea either at rest or during exertion, and the dyspnea score also correlates with reductions in FRC and ERV. Weight reduction should be encouraged in any symptomatic obese individual, since virtually all of the respiratory complications of obesity improve with even moderate weight loss.

Pro-fibrotic processes in human lung fibroblasts are driven by an autocrine/paracrine endothelinergic system

BACKGROUND AND PURPOSE

Since endothelin (ET) may act as pro-fibrotic mediator, expression and release of ET isoforms, their receptors and potential pro-fibrotic ET effects were studied in human lung fibroblasts.

EXPERIMENTAL APPROACH

MRC-5 and primary human lung fibroblasts (phLFb) were cultured. Expression of prepro-ET isoforms was determined by qPCR and release of ET-1 by elisa. ET receptor function was analysed by real-time measurement of dynamic mass redistribution (DMR). Incorporation of [(3) H]-thymidine was determined as measure of proliferation and that of [(3) H]-proline for collagen synthesis. Phospho-p42/44 MAP kinase was determined by Western blot.

KEY RESULTS

ET-1 is the predominant ET in human lung fibroblasts (hLF), and TGF-β caused a further, selective and sustained up-regulation of ET-1 resulting in increased extracellular ET-1 accumulation. hLFb express mRNA encoding ET-A and ET-B receptors. Expression of both receptors was confirmed at protein level. ET-1 induced marked DMR signals, an effect that involved ET-A and ET-B receptors. Stimulatory effects of ET-1 on hLFb proliferation and collagen synthesis were mediated exclusively via ET-A receptors. ET-1, again via ET-A receptors, induced rapid activation of ERK MAPK, shown to be a crucial cellular signal in ET-1-induced collagen synthesis. ET-1-induced activation of ERK and collagen synthesis was, in contrast to corresponding effect of a muscarinic agonist, largely insensitive to pertussis toxin.

CONCLUSIONS AND IMPLICATIONS

hLFb are endowed with all elements necessary to build a functional autocrine/paracrine endothelinergic system, which appears to drive pro-fibrotic airway and lung remodelling processes, effects for which only ET-A, but not ET-B receptors appear to be of significance.

The effect of the endothelin-1 receptor antagonist, bosentan, on patients with poorly controlled asthma: a 17-week, double-blind, placebo-controlled crossover pilot study

OBJECTIVE

To determine the effect of bosentan on subjects with poorly controlled asthma.

METHODS

This was a double-blind, placebo-controlled crossover pilot study. Subjects were poorly controlled on anti-inflammatory and long acting β-agonist therapy, and had a baseline forced expiratory volume in 1 second (FEV1) percent of predicted of 40 -70%. Subjects were randomized to receive either bosentan or placebo at the therapeutic dose of 125 mg twice a day for 4 weeks, and then crossed over to the alternate therapy. The asthma control test, asthma symptom scores, rescue albuterol use, and FEV1 were measured at baseline and during the last week of bosentan and placebo. Acute changes in FEV1 were measured after the initial therapeutic bosentan and placebo dose.

RESULTS

Seven of eleven randomized subjects completed the protocol. There was no difference in change in FEV1 after the bosentan phase when compared with placebo (+0.08 ± 0.31 L and +0.23 ± 0.26 L p = .34). Changes from baseline values in the asthma control test and asthma symptom scores were also similar in bosentan and placebo phases (+1.71 ± 3.99 and +4.57 ± 4.39 p = .16) and (+0.14 ± 9.3 and -0.29 ± 5.28 p = .93). Rescue β-agonist use did not change significantly during the last week of the bosentan phase when compared with placebo phase (-5.86 ± 0.94 puffs and -5.14 ± 16.85 puffs p = .94). Additionally, there was no difference in the change in FEV1 4 hours after bosentan 125 mg and placebo (-0.08 L ± 0.07 vs. +0.04 L ± 0.20 p = .20).

CONCLUSIONS

In this pilot study, 4 weeks of bosentan did not improve FEV1, β-agonist use, asthma symptom score, or asthma control test score in patients with poorly controlled asthma when compared with placebo.

Motility, survival, and proliferation

Airway smooth muscle has classically been of interest for its contractile response linked to bronchoconstriction. However, terminally differentiated smooth muscle cells are phenotypically plastic and have multifunctional capacity for proliferation, cellular hypertrophy, migration, and the synthesis of extracellular matrix and inflammatory mediators. These latter properties of airway smooth muscle are important in airway remodeling which is a structural alteration that compounds the impact of contractile responses on limiting airway conductance. In this overview, we describe the important signaling components and the functional evidence supporting a view of smooth muscle cells at the core of fibroproliferative remodeling of hollow organs. Signal transduction components and events are summarized that control the basic cellular processes of proliferation, cell survival, apoptosis, and cellular migration. We delineate known intracellular control mechanisms and suggest future areas of interest to pursue to more fully understand factors that regulate normal myocyte function and airway remodeling in obstructive lung diseases.

Bronchoconstriction in nonhuman primates: a species comparison

Bronchoconstriction is a characteristic symptom of various chronic obstructive respiratory diseases such as chronic obstructive pulmonary disease and asthma. Precision-cut lung slices (PCLS) are a suitable ex vivo model to study physiological mechanisms of bronchoconstriction in different species. In the present study, we established an ex vivo model of bronchoconstriction in nonhuman primates (NHPs). PCLS prepared from common marmosets, cynomolgus macaques, rhesus macaques, and anubis baboons were stimulated with increasing concentrations of representative bronchoconstrictors: methacholine, histamine, serotonin, leukotriene D₄ (LTD₄), U46619, and endothelin-1. Alterations in the airway caliber were measured and compared with previously published data from rodents, guinea pigs, and humans. Methacholine induced maximal airway constriction, varying between 74 and 88% in all NHP species, whereas serotonin was ineffective. Histamine induced maximal bronchoconstriction of 77 to 90% in rhesus macaques, cynomolgus macaques, and baboons and a lesser constriction of 53% in marmosets. LTD₄ was ineffective in marmosets and rhesus macaques but induced a maximum constriction of 44 to 49% in cynomolgus macaques and baboons. U46619 and endothelin-1 caused airway constriction in all NHP species, with maximum constrictions of 65 to 91% and 70 to 81%, respectively. In conclusion, PCLS from NHPs represent a valuable ex vivo model for studying bronchoconstriction. All NHPs respond to mediators relevant to human airway disorders such as methacholine, histamine, U46619, and endothelin-1 and are insensitive to the rodent mast cell product serotonin. Only PCLS from cynomolgus macaques and baboons, however, responded also to leukotrienes, suggesting that among all compared species, these two NHPs resemble the human airway mechanisms best.

Targeting abnormal airway vascularity as a therapeutical strategy in asthma

Asthma is a chronic inflammatory disease of airways, characterized by airway hyperresponsiveness and airflow limitation with acute bronchoconstriction, swelling of the airway wall, chronic mucus plug formation and airway wall remodelling. Functional and structural changes in the vasculature of asthmatic airways have been documented, and the signalling mechanisms are complex and have recently attracted much attention. The vascular changes may affect inflammatory cell recruitment, airway hyperresponsiveness and the regulation of airway calibre, and further, the level of disease control. Many critical factors are involved in the pathophysiological regulation of vascular changes in bronchial asthma, and the actions of these factors must be very carefully orchestrated. By better understanding the complicated actions of each factor, we may be able to advance further in asthma treatment.

Plasma and pulmonary fluid endothelin in horses with seasonal recurrent airway obstruction

BACKGROUND

Summer pasture-associated recurrent airway obstruction (SPA-RAO), a seasonal airway obstructive disease of horses, is characterized by clinical exacerbation after exposure to pasture during warm months of the year. Endothelin (ET)-1, potent bronchoconstrictor, mitogen, secretagogue, and proinflammatory mediator, has been implicated in the pathogenesis of asthma and equine heaves.

HYPOTHESIS

Immunoreactive ET-1 concentrations increase during clinical exacerbation and return to basal values during periods of disease remission.

ANIMALS

Twelve horses, 6 affected with SPA-RAO and 6 nonaffected.

METHODS

Prospective, observational study. Bronchoalveolar lavage fluid (BALF), arterial and venous plasma samples, and clinical variables were obtained from affected horses during clinical exacerbation and remission. Samples and data of nonaffected horses were collected during the summer and winter on dates similar to affected horses. Immunoreactive ET-1 was determined using a commercial ELISA.

RESULTS

The median and range ET-1 concentrations (pg/ml) in arterial (1.3, 0.7-1.8) and venous (1.3, 1.2-1.7) plasma and in BALF (0.3, 0.2-0.4), and pulmonary epithelial lining fluid (PELF) (25.5, 21-50) were greater in affected horses during clinical exacerbation compared with remission (P < .01). The concentrations of immunoreactive ET-1 were greater in affected horses during clinical exacerbation compared with nonaffected horses (P < .05).

CONCLUSIONS AND CLINICAL IMPORTANCE

During clinical exacerbation of SPA-RAO, ET-1 is increased in circulation and pulmonary secretions. Intervention with ET receptor antagonists should provide further information on the role of ET-1 in SPA-RAO.

Alteration of airway responsiveness mediated by receptors in ovalbumin-induced asthmatic E3 rats

AIM

Airway hyperresponsiveness is a constant feature of asthma. The aim of the present study was to investigate airway hyperreactivity mediated by contractile and dilative receptors in an ovalbumin (OVA)-induced model of rat asthma.

METHODS

Asthmatic E3 rats were prepared by intraperitoneal injection with OVA/aluminum hydroxide and then challenged with intranasal instillation of OVA-PBS two weeks later. The myograph method was used to measure the responses of constriction and dilatation in the trachea, main bronchi and lobar bronchi.

RESULTS

In asthmatic E3 rats, beta(2) adrenoceptor-mediated relaxation of airway smooth muscle pre-contracted with 5-HT was inhibited, and there were no obvious difference in relaxation compared with normal E3 rats. Contraction of lobar bronchi mediated by 5-HT and sarafotoxin 6c was more potent than in the trachea or main bronchi. Airway contractions mediated by the endothelin (ET)(A) receptor, ET(B) receptor and M(3) muscarinic receptor were augmented, and the augmented contraction was most obvious in lobar bronchi. The order of efficacy of contraction for lobar bronchi induced by agonists was ET-1, sarafotoxin 6c>ACh>5-HT. OX8 (an antibody against CD8(+) T cells) strongly shifted and OX35 (an antibody against CD4(+) T cells) modestly shifted isoprenaline-induced concentration-relaxation curves in a nonparallel fashion to the left with an increased R(max) in asthmatic rats and sarafotoxin 6c-induced concentration-contractile curves to the right with a decreased E(max).

CONCLUSION

The inhibition of airway relaxation and the augmentation of contraction mediated by receptors contribute to airway hyperresponsiveness and involve CD8(+) and CD4(+) T cells.Acta Pharmacologica Sinica (2009) 30: 965-972; doi: 10.1038/aps.2009.61.

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.

Regulation of endothelin-1-induced interleukin-6 production by Ca2+ influx in human airway smooth muscle cells

Endothelin-1 is considered to be an important mediator in the pathophysiology of asthma because it induces contraction, hypertrophy, and proliferation in airway smooth muscle cells as well as inflammatory responses in the airway. Airway smooth muscle cells have been suggested to contribute to airway inflammation in asthma by producing cytokines. Nevertheless, the role of intracellular Ca(2+) signal in cytokine production in human airway smooth muscle cells is still unclear. We investigated the mechanisms by which endothelin-1 induces production of interleukin (IL)-6, a pleiotropic cytokine, in primary cultured human airway smooth muscle cells. Levels of IL-6 protein and mRNA were significantly increased by endothelin-1 in dose- and time-dependent manners. Endothelin-1-induced IL-6 production was markedly attenuated by EGTA and various Ca(2+) channel inhibitors such as 3,5-bis(trifluoromethyl)-1H-pyrazole derivative (BTP-2), 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole hydrochloride (SKF96365), and nifedipine. Endothelin-1-induced increases in intracellular Ca(2+) concentrations were significantly inhibited in Ca(2+)-free solution and by BTP-2, SKF96365, and nifedipine. The IL-6 synthesis was also inhibited by the extracellular signal-regulated kinase (ERK)1/2 inhibitor 1,4-diamino-2,3-dicyano-1,4-bis(o-aminophenylmercapto)-butadiene ethanolate (U0126) and the p38 inhibitor 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole (SB203580), but not by the c-Jun NH2-terminal kinase inhibitor anthra[1,9-cd]-pyrazol-6-(2H)-one (SP600125). Endothelin-1 significantly upregulated phosphorylation of ERK1/2 and p38 but blocking Ca(2+) influx pathways did not inhibit either upregulation. These findings demonstrate that endothelin-1-induced IL-6 synthesis in airway smooth muscle cells occurs via two parallel but independent events that include Ca(2+) influx and activation of ERK1/2 and p38.

ETB receptor polymorphism is associated with airway obstruction

Background

Endothelin-1 (EDN1) has been involved in the development of airway obstruction and inflammation in asthma. Several polymorphisms have been identified among the genes encoding for preproET1, an inactive precursor of ET-1, and for ET_A (EDNRA) and ET_B (EDNRB), the two receptors for EDN1. In the present work, we hypothesised that molecular variation in these genes could be a major determinant of the degree of bronchial obstruction. The purpose of this study was to investigate whether the genetic polymorphisms of preproET-1, EDNRA and EDNRB genes were associated with the degree of airway obstruction, assessed by FEV₁.

Methods

Polymorphisms of preproET-1, EDNRA and EDNRB were first studied in a population of adult asthmatic patients. Results were confirmed in a large population of adults from the general population from the ECRHS II study.

Results

In our population of adult asthmatic patients, the EDNRB-30G>A (Leu277Leu) polymorphism (GG genotype) is strongly associated with a low FEV₁ and with a higher percentage of patients with FEV1 < 80% of predicted value. No relationship was found between pulmonary function and EDNRA-1363C>T (His323His) or preproET-1-595G>T (Lys198Asp) polymorphism. In the adult population from the ECRHS II, we found a similar association between GG genotype and a low FEV₁ or a higher percentage of subjects with FEV1 < 80% predicted, especially in the subgroups of asthmatics subjects (OR = 4.31 (95%CI 1.03 – 18.04)) and smokers (OR = 7.42 (95%CI 1.69 – 32.6)).

Conclusion

the EDNRB-30G>A polymorphism could be a determinant of airway obstruction in humans with predisposing factors such as tobacco smoke exposure or asthma.

Endothelin-1 induces hypertrophy and inhibits apoptosis in human airway smooth muscle cells

Endothelin-1 (ET-1), a G protein-coupled receptor-activating peptide, is increased in airway epithelium, plasma, and bronchoalveolar lavage fluid of asthmatic patients. We hypothesized that ET-1 may contribute to the increased airway smooth muscle mass found in severe asthma by inducing hypertrophy and inhibiting apoptosis of smooth muscle cells. To investigate this hypothesis, we determined that treatment of primary human bronchial smooth muscle cells with ET-1 dose dependently [10(-11)-10(-7) M] inhibited the apoptosis induced by serum withdrawal. ET-1 treatment also resulted in a significant increase in total protein synthesis, mediated through both ET(A) and ET(B) receptors, cell size, as well as increased expression of myosin heavy chain, alpha-smooth muscle actin, and calponin. ET-1-induced hypertrophy was accompanied by activation of JAK1/STAT-3 and MAPK1/2 (ERK1/2) cell signaling pathways. Inhibition of JAK1/STAT-3 pathways by piceatannol or ERK1/2 by the MAPK/ERK kinase 1/2 inhibitor U0126 blunted the increase in total protein synthesis. The hypertrophic effect of ET-1 was equivalent to that of the gp130 cytokine oncostatin M and greater than that induced by cardiotrophin-1. ET-1 induced release of IL-6 but not IL-11, leukemia inhibitory factor, oncostatin M, or cardiotrophin-1, although treatment of cells with IL-6 alone did not induce hypertrophy. These results suggest that ET-1 is a candidate mediator for the induction of increased smooth muscle mass in asthma and identify signaling pathways activated by this mediator.

The relationship between serum endothelin (ET)-1 and wheezing status in the children with Mycoplasma pneumoniae pneumonia

Although Mycoplasma pneumoniae infection is known to be associated with acute wheezing and the exacerbation of asthma, the mechanism by which this pathogen contributes to the development of wheeze-related symptoms is not fully understood. The aim of our study was to examine serum endothelin (ET)-1 and other cytokines in acute M. pneumoniae pneumonia and investigate if there is any relation between these inflammatory mediators and the occurrence of wheezing. We studied 53 patients, aged 3-13 yr, who admitted with pneumonia. These patients were divided into three groups: M. pneumoniae pneumonia with wheeze (n=23) and without wheeze (n=19), and the patients without the evidence of M. pneumoniae infection (n=11). Age-matched controls (n=10) were also studied. The serum concentrations of ET-1, interleukin (IL)-5 and IL-18 were measured using ELISA kits in patient groups and controls. The patients with M. pneumoniae pneumonia had significantly higher serum ET-1 than those without evidence of M. pneumoniae infection. In the presence of M. pneumoniae pneumonia, ET-1 concentrations were significantly higher in the patients with wheeze than those without wheeze. IL-5 and IL-18 in each patient group were higher compared to controls. However, no significant between-group difference was observed. Total serum IgE levels were significantly higher in the patients with M. pneumoniae pneumonia and wheeze than in those without wheeze. A positive correlation was observed between serum ET-1 and total IgE in the patients with M. pneumoniae pneumonia and wheeze. Our results may suggest a role of ET-1 in the occurrence of acute wheezing or exacerbation of asthma associated with M. pneumoniae pneumonia.

Reflex regulation of airway smooth muscle tone

Autonomic nerves in most mammalian species mediate both contractions and relaxations of airway smooth muscle. Cholinergic-parasympathetic nerves mediate contractions, whereas adrenergic-sympathetic and/or noncholinergic parasympathetic nerves mediate relaxations. Sympathetic-adrenergic innervation of human airway smooth muscle is sparse or nonexistent based on histological analyses and plays little or no role in regulating airway caliber. Rather, in humans and in many other species, postganglionic noncholinergic parasympathetic nerves provide the only relaxant innervation of airway smooth muscle. These noncholinergic nerves are anatomically and physiologically distinct from the postganglionic cholinergic parasympathetic nerves and differentially regulated by reflexes. Although bronchopulmonary vagal afferent nerves provide the primary afferent input regulating airway autonomic nerve activity, extrapulmonary afferent nerves, both vagal and nonvagal, can also reflexively regulate autonomic tone in airway smooth muscle. Reflexes result in either an enhanced activity in one or more of the autonomic efferent pathways, or a withdrawal of baseline cholinergic tone. These parallel excitatory and inhibitory afferent and efferent pathways add complexity to autonomic control of airway caliber. Dysfunction or dysregulation of these afferent and efferent nerves likely contributes to the pathogenesis of obstructive airways diseases and may account for the pulmonary symptoms associated with extrapulmonary disorders, including gastroesophageal reflux disease, cardiovascular disease, and rhinosinusitis.

Endothelin in health and disease

Endothelin is a recently discovered peptide composed of 21 amino acids. There are three endothelin isomers: endothelin-1 (ET-1), endothelin-2 (ET-2) and endothelin- 3 (ET-3). In humans and animals levels of ET-1, ET-2, ET-3 and big endothelin in blood range from 0,3 to 3 pg/ml. ET-1, ET-2 and ET-3 act by binding to receptors. Two main types of the receptors for endothelins exist and they are referred to as A and B type receptors. Different factors can stimulate or inhibit production of endothelin by endothelial cells. Mechanical stimulation of endothelium, thrombin, calcium ions, epinephrine, angiotensin II, vasopressin, dopamine, cytokines, growth factors stimulate the production of endothelin whereas nitric oxide, cyclic guanosine monophosphate, atrial natriuretic peptide, prostacyclin, bradykinin inhibit its production. Endothelins have different physiological roles in human body but at the same time their actions are involved in the pathogenesis of many diseases. The aim of this review was to present some of, so far, the best studied physiological roles of endothelin and to summarize evidence supporting the potential role of ET in the pathogenesis of certain diseases.

Interleukin-1beta attenuates endothelin B receptor-mediated airway contractions in a murine in vitro model of asthma: roles of endothelin converting enzyme and mitogen-activated protein kinase pathways

BACKGROUND

Asthma is a chronic airway disease, known to involve several inflammatory mediators. Little is known about how these mediators interact in order to produce or attenuate even basic features of the disease, like airway hyper-reactivity and remodelling. Endothelin-1 (ET-1) and IL-1beta are two mediators suggested to play important roles in the induction of airway inflammation.

OBJECTIVE

To investigate the interactions between ET-1 and IL-1beta, using a novel in vitro model of asthma, focusing on airway smooth muscle contractility.

METHODS

Isolated murine tracheal segments were cultured from 1 to 8 days in the absence and presence of IL-1beta. The subsequent contractile responses to sarafotoxin 6c (S6c) (selective agonist for ETB receptor) and sarafotoxin 6b (S6b) (ETA and ETB receptor agonist) were recorded by a myographs system. In all experiments, ETB receptors were desensitized before the contractile response to S6b was recorded. Thus, the response to S6b is only mediated by ETA receptors in the present study. The mRNA expressions for ET-1 and endothelin (ET) receptors were quantified by real-time PCR.

RESULTS

Organ culture in the presence of IL-1beta attenuated the maximal contraction induced by S6c, but not S6b. This reduction was concentration-dependent and was significant after 2, 4 and 8 days of culture. To investigate the mechanisms behind this, inhibitors for endothelin converting enzyme (ECE) phosphoramidon, c-JUN N-terminal kinase (JNK) SP600125, extracellular-signal-regulated kinase 1/2(ERK 1/2) PD98059 and p38 pathway SB203580 were used. Individually, SP600125 and PD98059, but not SB203580, could partly reverse the reduction induced by IL-1beta. An additional effect was obtained when SP600125 and PD98059 were combined. The mRNA expressions for ET-1 and ETB receptor were up- and down-regulated, respectively, by IL-1beta.

CONCLUSION

Presence of IL-1beta in the airways attenuate the contractile response mediated via ETB receptors, an effect dependent on ECE, JNK and ERK 1/2 pathways.

Up-Regulation of Endothelin Receptor Function and mRNA Expression in Airway Smooth Muscle Cells Following Sephadex-Induced Airway Inflammation

The hypothesis that up-regulation of bronchial constrictor endothelin receptors in airway smooth muscle cells may contribute to hyperreactivity during airway inflammation was tested in the present study by quantitative endothelin receptor mRNA analysis and functional responses in ring segments of rat trachea and bronchi. Real time reverse transcription polymerase chain reaction was used to quantify endothelin receptor expression in rat airway smooth muscle cells following Sephadex-induced inflammation. Compared with controls, Sephadex-induced airway inflammation caused a significant increase (3.9 times P<0.05) of endothelin receptor type B mRNA expression in bronchial smooth muscle cells, but not in tracheal smooth muscle cells. Functional myograph studies of bronchial and tracheal ring segments without epithelium (mechanically denuded) revealed an increase of the maximum contractile effects of endothelin-1 (a dual agonist for both endothelin type A and B receptors) and sarafotoxin 6c (a selective agonist for endothelin B receptors) in bronchial smooth muscle cells in Sephadex-induced inflammation, but not in tracheal smooth muscle cells. The enhanced maximal responses of bronchial smooth muscle cells to endothelin-1 and sarafotoxin 6c in Sephadex-induced inflammation support our molecular findings and hence imply a role for endothelin B receptors in airway hyperreactivity during airway inflammation.

Estradiol in premenstrual asthma: a double-blind, randomized, placebo-controlled, crossover study

STUDY OBJECTIVES

To characterize asthma symptoms and pulmonary function throughout two menstrual cycles, with and without exogenous estradiol administration, in women with premenstrual asthma, and to determine the effect of estradiol administration on asthma symptoms, pulmonary function, quality of life, and biomarkers of airway inflammation.

DESIGN

Double-blind, randomized, placebo-controlled, crossover study.

SETTING

Respiratory clinic and clinical research center.

SUBJECTS

Twelve women with documented premenstrual asthma (> or = 20% premenstrual worsening of asthma symptoms and/or of peak expiratory flow [PEF] during a 1-month screening phase).

INTERVENTION

Each woman received either estradiol 2 mg or placebo orally between cycle days 23 and 28 (i.e., premenstrually, or before the onset of menses) in the first cycle and then crossed over to the other arm in the second cycle. Throughout both cycles, the women recorded daily morning and evening PEF readings and asthma symptoms.

MEASUREMENTS AND MAIN RESULTS

Spirometry testing and measurement of serum estradiol and biomarkers of airway inflammation were performed on days 8 (follicular phase), 22 (luteal phase), and 28 (premenstrually) of both the estradiol and placebo cycles. During the two premenstrual visits, the Asthma Quality of Life Questionnaire was administered. No notable differences were observed between the estradiol and placebo cycles in daily PEF recordings or composite asthma symptoms scores. The area under the curve (AUC) for the composite asthma symptoms versus time profile was numerically, but not statistically, lower (denoting less severe symptoms) during the estradiol cycle than during the placebo cycle. Likewise, no significant difference in AUC values for morning PEF or evening PEF was found between the estradiol cycle and the placebo cycle. Despite differences (p<0.05) in day-28 estradiol concentrations for estradiol and placebo cycles, no significant differences were found in forced expiratory volume in 1 second, serum endothelin-1, serum and urine eosinophil protein X, urine leukotriene E4, or quality-of-life scores.

CONCLUSION

Exogenously administered estradiol did not have a significant effect in women with premenstrual asthma whose asthma was classified predominantly as mild and under excellent control. As in the case of premenstrual syndrome, the placebo effect may be prominent in premenstrual asthma. Further trials, involving women with more severe asthma under poorer control, are warranted to discern underlying mechanisms for the worsening of asthma in relation to menstruation.

Endothelin-induced vascular and bronchial effects in pig airways: role in acute allergic responses

The effects of endothelin (ET) agonists on airway mechanics and bronchial blood flow were studied as well as the effects of mixed ET-receptor antagonist bosentan on allergen-induced airway reactions in the pig. ET agonists [ET-1, ET-3, and the ET(B) receptor-selective agonist Sarafotoxin 6c (Sf6c)] were given as intravenous injections (0.4-200 pmol/kg) to eight anesthetized pigs. Bosentan (10 mg/kg iv) was then administered, and the injections were repeated. Only Sf6c caused a significant increase in airway resistance, and this response was blocked by bosentan. Sf6c and ET-1 (200 and 400 pmol/kg, respectively) were also given as aerosols to five pigs. Sf6c, but not ET-1, caused bronchoconstriction via this route. All agonists (intravenous) caused increases in bronchial vascular conductance, an effect that was blocked by an NO-synthase inhibitor (N(G)-nitro-L-arginine) but unaffected by a cyxlooxygenase inhibitor (diclofenac). Fourteen pigs were sensitized with ascaris suum antigen. Under anesthesia, eight pigs were pretreated with bosentan, and six pigs were controls. They were all challenged with allergen aerosol resulting in acute bronchoconstriction and elevation of ET-1 in bronchoalveolar lavage fluid. Bosentan did not affect the maximal acute airway obstruction but markedly increased baseline bronchial vascular conductance, suggesting a basal vascular tone regulated by ETs. In conclusion, ETs induce bronchoconstriction primarily via the ET(B) receptor in the pig. However, ETs are probably not involved in the allergen-induced acute bronchoconstriction in this model.

An endothelin receptor antagonist, SB-217242, inhibits airway hyperresponsiveness in allergic mice

Within the airways, endothelin-1 (ET-1) can exert a range of prominent effects, including airway smooth muscle contraction, bronchial obstruction, airway wall edema, and airway remodeling. ET-1 also possesses proinflammatory properties and contributes to the late-phase response in allergic airways. However, there is no direct evidence for the contribution of endogenous ET-1 to airway hyperresponsiveness in allergic airways. Allergic inflammation induced in mice by sensitization and challenge with the house dust mite allergen Der P1 was associated with elevated levels of ET-1 within the lung, increased numbers of eosinophils within bronchoalveolar lavage fluid and tissue sections, and development of airway hyperresponsiveness to methacholine (P < 0.05, n = 6 mice per group). Treatment of allergic mice with an endothelin receptor antagonist, SB-217242 (30 mg x kg(-1) x day(-1)), during allergen challenge markedly inhibited airway eosinophilia (bronchoalveolar lavage fluid and tissue) and development of airway hyperresponsiveness. These findings provide direct evidence for a mediator role for ET-1 in development of airway hyperresponsiveness and airway eosinophilia in Der P1-sensitized mice after antigen challenge.

Plasma endothelin-1 immunoreactivity in asthmatic children

BACKGROUND

Endothelin-1 (ET-1) has been formerly demonstrated to have potent vasocontractile as well as bronchoconstrictor effects in vitro. This followup study was aimed to evaluate the possible changes in ET-1 levels in the plasma of asthmatic children, according to disease activity and severity.

METHODS

Plasma ET-1 was estimated by enzyme-linked immunoadsorbent assay in 30 asthmatic patients (6 to 12 years old) during and after remission of an acute attack. Thirty age- and sex-matched healthy children were included as a control group.

RESULTS

Plasma ET-1 immunoreactivity was significantly increased in the asthmatic children during the attacks (17.2+/-6.9 pg/mL) in comparison to the levels during quiescence of symptoms (0.9+/-1.13 pg/mL). Further, both values were significantly higher than the control value (0.22+/-0.29 pg/mL). The severity of attacks as judged clinically and by peak expiratory flow rate measurement did not influence the plasma endothelin status; neither did the family history of atopy nor the absolute eosinophil count. However, serum total IgE levels could be positively correlated to the plasma endothelin concentrations measured after remission of the asthmatic attacks (P < 0.05).

CONCLUSIONS

Our findings reinforce the concept that ET-1 may be implicated in the pathogenesis of bronchoconstriction. This may encourage further studies on the value of ET-1 antagonism among alternative therapeutic modalities of childhood asthma.

Role of endothelin-1 in lung disease

Endothelin-1 (ET-1) is a 21 amino acid peptide with diverse biological activity that has been implicated in numerous diseases. ET-1 is a potent mitogen regulator of smooth muscle tone, and inflammatory mediator that may play a key role in diseases of the airways, pulmonary circulation, and inflammatory lung diseases, both acute and chronic. This review will focus on the biology of ET-1 and its role in lung disease.

Endothelin in health and disease: endothelin receptor antagonists in the management of pulmonary artery hypertension

Endothelin (ET) has been identified as playing a fundamental role in many disease processes. Therapeutic efforts at interrupting ET's pathologic effects have focused on endothelin receptor antagonists (ERAs), of which two, bosentan and sitaxsentan, have been evaluated for the treatment of both primary and secondary pulmonary arterial hypertension (PAH). We discuss the multiple actions of ET, its role in various disease states, and the effects of ET receptor stimulation and blockade. Current classification and management of PAH are reviewed, along with the promise of greatly improved treatment generated by recent and ongoing clinical trials using ERAs.

Endothelin system: the double-edged sword in health and disease

The endothelin system consists of two G-protein-coupled receptors, three peptide ligands, and two activating peptidases. Its pharmacological complexity is reflected by the diverse expression pattern of endothelin system components, which have a variety of physiological and pathophysiological roles. In the vessels, the endothelin system has a basal vasoconstricting role and participates in the development of diseases such as hypertension, atherosclerosis, and vasospasm after subarachnoid hemorrhage. In the heart, the endothelin system affects inotropy and chronotropy, and it mediates cardiac hypertrophy and remodeling in congestive heart failure. In the lungs, the endothelin system regulates the tone of airways and blood vessels, and it is involved in the development of pulmonary hypertension. In the kidney, it controls water and sodium excretion and acid-base balance, and it participates in acute and chronic renal failure. In the brain, the endothelin system modulates cardiorespiratory centers and the release of hormones. More advanced functional analysis of the endothelin system awaits not only additional pharmacological studies using highly specific endothelin antagonists but also the generation of genetically altered rodent models with conditional loss-of-function and gain-of-function manipulations.

Effect of endothelin antagonism on the production of cytokines in eosinophilic airway inflammation

Endothelin (ET)-1 has been launched as an important mediator in bronchial asthma, which is an eosinophilic airway inflammation. However, the interplay between ET-1 and other proinflammatory mediators during the development of airway inflammation has not been elucidated. We wanted to study 1) whether the production of ET-1 precedes the production of other proinflammatory mediators and 2) whether ET-1 stimulates the production of these mediators within the airways. These hypotheses were studied during the development of an eosinophilic airway inflammation in rats. The increase in ET-1 mRNA level in lung tissue preceded the increase in mRNA levels of tumor necrosis factor-alpha, interleukin (IL)-1beta, and IL-8. Treatment of the animals with the ET receptor antagonist bosentan resulted in a substantial decrease in the concentrations of tumor necrosis factor-alpha, IL-4, IL-1beta, interferon-gamma, and ET-1 in bronchoalveolar lavage fluid. In conclusion, the synthesis of ET-1 as measured by increased mRNA level precedes the synthesis of other proinflammatory cytokines of importance for the development of an eosinophilic airway inflammation, and ET antagonism inhibits the production of these mediators within the airways. Whether treatment with ET antagonists will prove beneficial for patients with eosinophilic airway inflammations like bronchial asthma is not yet known.

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.

Effect of a novel bifunctional endothelin receptor antagonist, IRL 3630A, on guinea pig respiratory mechanics

This study characterized the in vitro pharmacological properties of a newly developed endothelin receptor antagonist, N-butanesulfonyl-[N-(3, 5-dimethylbenzoyl)-N-methyl-3-[4-(5-isoxazolyl)-phenyl]-(D)- alanyl]-( L)-valineamide sodium salt (IRL 3630A), and its in vivo effects on respiratory mechanics were determined. IRL 3630A showed highly balanced affinities to human endothelin ET(A) and ET(B) receptors, giving apparent K(i) values of 1.5 and 1.2 nM, respectively. This compound also potently antagonized the endothelin-1-induced intracellular Ca(2+) increases in both embryonic bovine tracheal (EBTr) cells expressing endothelin ET(A) receptors and human Girardi heart (hGH) cells expressing endothelin ET(B) receptors. In guinea pig isolated tracheas having both endothelin ET(A) and ET(B) receptors, IRL 3630A greatly inhibited endothelin-1-induced contraction (pA(2)=7.1), which was partially or scarcely suppressed by the endothelin ET(A) receptor antagonist cyclo[-(D)-Trp-(D)-Asp-(L)-Pro-(D)-Val-(L)-Leu-] (BQ-123) or the endothelin ET(B) receptor antagonist N-(3, 5-dimethylbenzoyl)-N-methyl-3-(4-phenyl)-(D)-phenylalanyl-(L)-t ryptop han (IRL 2500), respectively. Bolus i.v. injections of IRL 3630A administered into anaesthetized guinea pigs at 10 and 30 microg/kg inhibited endothelin-1 (1.3 microg/kg)-induced changes in respiratory resistance and compliance in a dose dependent manner, whereas both sodium 2-benzo[1, 3]dioxol-5-yl-4-(4-methoxy-phenyl)-4-oxo-3-(3,4, 5-trimethoxy-benzyl)-but-2-enoate (an endothelin ET(A) receptor antagonist: PD 156707) and IRL 2500 at doses of up to 30 microg/kg did not affect endothelin-1-induced changes in respiratory mechanics, reflecting the in vitro results. IRL 3630A is thus an effective bifunctional endothelin receptor antagonist, and will be useful in clarifying the role of endothelin in pulmonary diseases such as bronchial asthma.

Arterial and bronchoalveolar lavage fluid endothelin-1 concentration in asthma

Endothelins are a family of peptide mediators that have a number of biological properties, including the ability to act as bronchoconstrictors and vasoconstrictors of isolated airways and vessels. Endothelin-1 (ET-1) is the more potent peptide compared with the other two peptides of the family. To examine a possible involvement of ET- 1 in the pathogenesis of asthma, we measured arterial ET-1 levels in 11 patients with atopic asthma during attack and during remission, and in 11 healthy control subjects. We also performed fiberoptic bonchoscopy and bronchoalveolar lavage (BAL) to measure ET-1 levels in the 11 asthmatic patients during remission, and in the 11 healthy control subjects. ET-1 concentrations in arterial blood and in BAL were measured by a radioimmunoassay method. Arterial ET-1 levels were very significantly higher in asthma attack (3.67 +/- 0.51 pg ml(-1)) and in asthma remission (2.65 +/- 10.62 pg ml(-1)) compared with those of the healthy controls (1.37 +/- 0.14 pg ml(-1)) (P < 0.001). Arterial ET-1 levels were also very significantly higher during asthma attack compared with those in asthma remission (P < 0.001). BAL ET-1 levels were significantly higher in asthma remission (0.73 +/- 0.53 pmol g(-1)) compared with those of the healthy controls (0.16 +/- 0.02 pmol g(-1)) (P < 0.05). No correlation was observed between arterial and BAL ET-1 levels, PaO2 and peak expiratory flow rate (PEFR). These data are consistent with the hypothesis that ET-1 contributes to the pathophysiology of asthma. However, it is likely that the true importance of this vasoconstrictor peptide will only be revealed by pharmacological studies with specific receptor antagonists.

Hypoxia augments conversion of big-endothelin-1 and endothelin ET(B) receptor-mediated actions in rat lungs

We have examined the effect of endothelin-1, sarafotoxin-6C, big-endothelin-1 and other agents on perfused lungs from chronically hypoxic rats. Increases in pulmonary perfusion pressure induced by big-endothelin-1, endothelin-1, phenylephrine and potassium chloride were enhanced in hypoxic lungs, while the constrictor action of sarafotoxin-6C was not increased. When basal pulmonary perfusion pressure was raised, low doses of endothelin-1 and sarafotoxin-6C produced decreases in pulmonary perfusion pressure which were significantly greater in chronically hypoxic lungs, whereas responses to sodium nitroprusside were unchanged. Endothelin ET(B) receptor-mediated bronchoconstrictor responses were also potentiated in hypoxic lungs, whereas responses to carbachol were not. In hypoxic lungs, conversion of big-endothelin-1 to endothelin-1 was significantly increased. These data provide evidence for a generalised increase in vasomotor activity in chronically hypoxic lungs, and a more selective increase in endothelin ET(B) receptor-mediated vasodilator and bronchoconstrictor responses. Hypoxia also augments the conversion of big-endothelin-1 to endothelin-1.

Cellular signaling by the potent bronchoconstrictor endothelin-1 in airway smooth muscle

OBJECTIVE

The objective of this study was to determine whether the potent bronchoconstrictor endothelin-1 was coupled to the activation of the inositol phosphate and/or inhibition of the cyclic adenine monophosphate second messenger pathways in porcine airway smooth muscle.

DESIGN

Prospective, controlled, in vitro, nonblinded study.

SETTING

University biochemical and molecular biological research laboratory.

SUBJECTS

Pigs of both genders.

INTERVENTIONS

Airway smooth muscle was dissected from the trachea of pigs exsanguinated under anesthesia. Airway smooth muscle from six animals preloaded with 3H-myoinositol was exposed to endothelin-1, carbachol (positive control) or vehicle for 30 mins. Some tissues were pretreated with antagonists selective for the ET(A) (BQ-485) and ET(B) (BQ-788) endothelin receptor subtypes. Newly synthesized 3H-inositol phosphates were recovered by column chromatography. Airway smooth muscle from an additional 7 pigs was homogenized and incubated in the presence of 32P-alpha-adenosine triphosphate, guanosine triphosphate (GTP) and either carbachol or endothelin to measure the inhibitory influence of carbachol (positive control) or endothelin on GTP-stimulated adenylyl cyclase activity. Newly synthesized 32P-cyclic adenosine monophosphate was isolated by sequential column chromatography over Dowex and alumina.

MEASUREMENTS AND MAIN RESULTS

Total inositol phosphates increased in porcine airway smooth muscle in response to either carbachol or endothelin. The endothelin receptor antagonist BQ-485 (ET(A) selective) but not BQ-788 (ET(B) selective) dose-dependently inhibited endothelin-1 induced inositol phosphate accumulation. In adenylyl cyclase assays, carbachol (positive control), but not endothelin-1, significantly inhibited GTP-stimulated adenylyl cyclase activity.

CONCLUSION

Endothelin-1 couples to the activation of the inositol phosphate pathway via the ET(A) receptor subtype but does not couple to inhibition of the adenylyl cyclase pathway in porcine airway smooth muscle. The potent bronchoconstrictive effects of endothelin likely involve the acute activation of the inositol phosphate pathway in airway smooth muscle.

Endothelin-1 impairs neutrophil respiratory burst and elimination of Escherichia coli in rabbits

OBJECTIVE

During systemic inflammation, elevated levels of endothelin (ET)-1 have been reported. The aim of this study was to investigate the effects of ET-1 on neutrophil (PMN) respiratory burst, phagocytosis, and elimination of Escherichia coli from blood and tissues.

DESIGN

Prospective, randomized, controlled trial.

SETTING

Experimental laboratory in a university hospital.

SUBJECTS

A total of 18 female chinchilla rabbits.

INTERVENTIONS

To quantify the clearance process, defined numbers (10(8) colony-forming units) of E. coli were injected intravenously into anesthetized rabbits, 60 mins after onset of continuous 0.2 microg/kg/min ET-1 administration (n = 9) and after saline infusion (control group, n = 9), respectively. To evaluate potential effects of ET-1 on bacterial elimination and killing, blood clearance of E. coli and colonization of different organs were investigated.

MEASUREMENTS

Variables monitored were neutrophil respiratory burst and phagocytosis activity, rates of bacterial elimination from the blood, arterial blood pressure, blood gases, serum lactate concentrations, and nitrite and nitrate levels. The animals were killed 3 hrs after bacterial injection and tissue samples of liver, kidney, spleen, and lung were collected for bacterial counts.

MAIN RESULTS

Compared with the control group, ET-1 significantly impaired PMN respiratory burst (p < .05) and prolonged elimination of injected E. coli from the blood (p < .01), whereas phagocytosis functions remained unaltered. The reduced PMN burst activity after ET-1 was associated with a higher bacterial colonization of all organs (lung, p < .01; spleen, p < .05). Endothelin-1 induced increases in mean arterial pressure (p < .01) and serum lactate concentrations, whereas nitrite and nitrate levels remained unaltered.

CONCLUSION

Endothelin-1 impairs respiratory burst and bacterial clearance from the blood and tissue. Thus, elevated levels of ET-1 during sepsis could induce organ hypoperfusion and cause disturbances in immune functions, increasing the risk of bacterial infections.