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

Azithromycin Partially Mitigates Dysregulated Repair of Lung Allograft Small Airway Epithelium

BACKGROUND

Dysregulated airway epithelial repair following injury is a proposed mechanism driving posttransplant bronchiolitis obliterans (BO), and its clinical correlate bronchiolitis obliterans syndrome (BOS). This study compared gene and cellular characteristics of injury and repair in large (LAEC) and small (SAEC) airway epithelial cells of transplant patients.

METHODS

Subjects were recruited at the time of routine bronchoscopy posttransplantation and included patients with and without BOS. Airway epithelial cells were obtained from bronchial and bronchiolar brushing performed under radiological guidance from these patients. In addition, bronchial brushings were also obtained from healthy control subjects comprising of adolescents admitted for elective surgery for nonrespiratory-related conditions. Primary cultures were established, monolayers wounded, and repair assessed (±) azithromycin (1 µg/mL). In addition, proliferative capacity as well as markers of injury and dysregulated repair were also assessed.

RESULTS

SAEC had a significantly dysregulated repair process postinjury, despite having a higher proliferative capacity than large airway epithelial cells. Addition of azithromycin significantly induced repair in these cells; however, full restitution was not achieved. Expression of several genes associated with epithelial barrier repair (matrix metalloproteinase 7, matrix metalloproteinase 3, the integrins β6 and β8, and β-catenin) were significantly different in epithelial cells obtained from patients with BOS compared to transplant patients without BOS and controls, suggesting an intrinsic defect.

CONCLUSIONS

Chronic airway injury and dysregulated repair programs are evident in airway epithelium obtained from patients with BOS, particularly with SAEC. We also show that azithromycin partially mitigates this pathology.

New perspectives in bronchial asthma: pathological, immunological alterations, biological targets, and pharmacotherapy

Asthma is the most common, long-lasting inflammatory airway disease that affects more than 10% of the world population. It is characterized by bronchial narrowing, airway hyperresponsiveness, vasodilatation, airway edema, and stimulation of sensory nerve endings that lead to recurring events of breathlessness, wheezing, chest tightness, and coughing. It is the main reason for global morbidity and occurs as a result of the weakening of the immune system in response to exposure to allergens or environmental exposure. In asthma condition, it results in the activation of numerous inflammatory cells like the mast and dendritic cells along with the accumulation of activated eosinophils and lymphocytes at the inflammation site. The structural cells such as airway epithelial cells and smooth muscle cells release inflammatory mediators that promote the bronchial inflammation. Long-lasting bronchial inflammation can cause pathological alterations, viz. the improved thickness of the bronchial epithelium and friability of airway epithelial cells, epithelium fibrosis, hyperplasia, and hypertrophy of airway smooth muscle, angiogenesis, and mucus gland hyperplasia. The stimulation of bronchial epithelial cell would result in the release of inflammatory cytokines and chemokines that attract inflammatory cells into bronchial airways and plays an important role in asthma. Asthma patients who do not respond to marketed antiasthmatic drugs needed novel biological medications to regulate the asthmatic situation. The present review enumerates various types of asthma, etiological factors, and in vivo animal models for the induction of asthma. The underlying pathological, immunological mechanism of action, the role of inflammatory mediators, the effect of inflammation on the bronchial airways, newer treatment approaches, and novel biological targets of asthma have been discussed in this review.

Endothelin-1 mediates Aspergillus fumigatus-induced airway inflammation and remodelling

BACKGROUND

Asthma is a chronic inflammatory condition of the airways and patients sensitized to airborne fungi such as Aspergillus fumigatus have more severe asthma. Thickening of the bronchial subepithelial layer is a contributing factor to asthma severity for which no current treatment exists. Airway epithelium acts as an initial defence barrier to inhaled spores, orchestrating an inflammatory response and contributing to subepithelial fibrosis.

OBJECTIVE

We aimed to analyse the production of pro-fibrogenic factors by airway epithelium in response to A fumigatus, in order to propose novel anti-fibrotic strategies for fungal-induced asthma.

METHODS

We assessed the induction of key pro-fibrogenic factors, TGF-β1, TGF-β2, periostin and endothelin-1, by human airway epithelial cells and in mice exposed to A fumigatus spores or secreted fungal factors.

RESULTS

Aspergillus fumigatus specifically caused production of endothelin-1 by epithelial cells in vitro but not any of the other pro-fibrogenic factors assessed. A fumigatus also induced endothelin-1 in murine lungs, associated with extensive inflammation and airway remodelling. Using a selective endothelin-1 receptor antagonist, we demonstrated for the first time that endothelin-1 drives many features of airway remodelling and inflammation elicited by A fumigatus.

CONCLUSION

Our findings are consistent with the hypothesis that elevated endothelin-1 levels contribute to subepithelial thickening and highlight this factor as a possible therapeutic target for difficult-to-treat fungal-induced asthma.

Targeting matrix metalloproteinase-13 in bronchial epithelial repair

BACKGROUND

Viral infection of the bronchial epithelium disrupts the barrier properties of the epithelium in healthy individuals and those with lung disease. Repair of the bronchial epithelium is dependent of the formation of a provisional fibrin matrix and migration of epithelial cells to cover denuded areas, followed by proliferation and differentiation.

OBJECTIVE

The objective was to test the hypothesis that poly I:C, a model of viral infection, limits epithelial repair through the stimulated release of matrix metalloproteinase-13 (MMP-13).

METHODS

Confluent layers of cultured normal human primary bronchial epithelial cells (NHBE) and SV-40 virus-transformed 16HBE14o- bronchial epithelial cells were mechanically wounded, and video microscopy used to measure the rate of wound closure over 2 hours, in the absence and presence of poly I:C (1-20 μg/mL). MMP-13, tissue factor and endothelin release were measured by ELISA. The effect of inhibitors of MMP-13 activity and expression and a nonspecific endothelin receptor antagonist, bosentan, on the rate of epithelial repair was investigated.

RESULTS

Poly I:C limited the rate of epithelial repair, and NHBE were significantly more sensitive to poly I:C effects than 16HBE14o- cells. NHBE, but not 16HBE14o-, released MMP-13 in response to poly I:C. Inhibitors of MMP-13 activity (WAY 170523) and expression (dimethyl fumarate) significantly enhanced the rate of repair. Bosentan enhanced the rate of bronchial epithelial repair by a mechanism that was independent of MMP-13.

CONCLUSIONS AND CLINICAL RELEVANCE

Bronchial epithelial repair is limited by endothelin and by MMP-13, a protease that degrades coagulation factors, such as fibrinogen, and matrix proteins essential for epithelial repair. Further studies with primary cells from patients are needed to confirm whether repurposing bosentan and inhibitors of MMP-13 expression or activity, for inhalation may be a useful therapeutic strategy in diseases where repeated cycles of epithelial injury and repair occur, such as asthma and COPD.

Knowledge translation: airway epithelial cell migration and respiratory diseases

Airway epithelial cell migration is essential for lung development and growth, as well as the maintenance of respiratory tissue integrity. This vital cellular process is also important for the repair and regeneration of damaged airway epithelium. More importantly, several lung diseases characterized by aberrant tissue remodeling result from the improper repair of damaged respiratory tissue. Epithelial cell migration relies upon extracellular matrix molecules and is further regulated by numerous local, neuronal, and hormonal factors. Under inflammatory conditions, cell migration can also be stimulated by certain cytokines and chemokines. Many well-known environmental factors involved in the pathogenesis of chronic lung diseases (e.g., cigarette smoking, air pollution, alcohol intake, inflammation, viral and bacterial infections) can inhibit airway epithelial cell migration. Further investigation of cellular and molecular mechanisms of cell migration with advanced techniques may provide knowledge that is relevant to physiological and pathological conditions. These studies may eventually lead to the development of therapeutic interventions to improve lung repair and regeneration and to prevent aberrant remodeling in the lung.

ETAR antagonist ZD4054 exhibits additive effects with aromatase inhibitors and fulvestrant in breast cancer therapy, and improves in vivo efficacy of anastrozole

Endothelin-1 (ET-1) and endothelin A receptor (ETAR) contribute to the development and progression of breast carcinomas by modulating cell proliferation, angiogenesis, and anti-apoptosis. We investigated antitumoral effects of the specific ETAR antagonist ZD4054 in breast cancer cells and xenografts, and assessed antitumoral efficacy of the combinations of ZD4054 with aromatase inhibitors and fulvestrant. Gene expression changes were assessed by quantitative real-time PCR. Cell proliferation was measured using alamarBlue; migration and invasion assays were performed using modified Boyden chambers. Evaluating the antitumoral efficacy of ZD4054 in vivo, different breast cancer models were employed using nude mice xenografts. ZD4054 reduced ET-1 and ETAR expression in MCF-7, MDA-MB-231, and MDA-MB-468 breast cancer cells in a concentration-dependent manner. ZD4054 inhibited invasion by up to 37.1% (P = 0.022). Combinations of ZD4054 with either anastrozole or letrozole produced significant reductions in migration of aromatase-overexpressing MCF-7aro cells (P < 0.05). Combination of ZD4054 with fulvestrant reduced MCF-7 cell migration and invasion by 36.0% (P = 0.027) and 56.7% (P < 0.001), respectively, with effects significantly exceeding those seen with either compound alone. Regarding tumor volume reduction in vivo, ZD4054 (10 mg/kg) was equipotent to fulvestrant (200 mg/kg) and exhibited additive effects with anastrozole (0.5 mg/kg). These data are the first indicating that selective ETAR antagonism by ZD4054 displays antitumoral activity on breast cancer cells in vitro and in vivo. Our data strongly support a rationale for the clinical use of ZD4054 in combination with endocrine therapies.

Inorganic arsenic as a developmental toxicant: in utero exposure and alterations in the developing rat lungs

In the present study, we characterize the toxic effects of in utero arsenic exposure on the developing lung. We hypothesize that in utero exposure to inorganic arsenic through maternal drinking water causes altered gene and protein expression in the developing lung, indicative of downstream molecular and functional changes. From conception to embryonic day 18, we exposed pregnant Sprague-Dawley rats to 500 ppb arsenic (as arsenite) via the drinking water. Subtracted cDNA libraries comparing control to arsenic exposed embryonic lungs were generated. In addition, a broad Western blot analysis was performed to identify altered protein expression. A total of 59 genes and 34 proteins were identified as being altered. Pathway mapping and analysis showed that cell motility was the process most affected. The most likely affected pathway was alteration in integrin signaling through the beta-catenin pathway, altering c-myc. The present study shows that arsenic induces alterations in the developing lung. These data may be useful in the elucidation of molecular targets and biomarkers of arsenic exposure during lung development and may aid in understanding the etiology of arsenic induced adult respiratory disease and lung cancers.

Endothelin-1 in exhaled breath condensate of stable and unstable asthma patients

Endothelins are proinflammatory, profibrotic, broncho- and vasoconstrictive peptides, which play an important role in the development of airway inflammation and remodeling in asthma. The study was undertaken to evaluate the endothelin-1 (ET-1) levels in exhaled breath condensate (EBC) of asthmatics with different degree in asthma severity. EBC was collected from 31 patients with allergic asthma (11 with steroid-naïve mild asthma, 10 with ICS-treated, stable mild-to-moderate asthma, 10 with ICS-treated unstable, severe asthma) and 7 healthy volunteers. In the three groups of asthmatics, ET-1 concentrations in EBC were significantly higher than in healthy volunteers. ET-1 levels were significantly higher in patients with unstable asthma than in the two groups with stable disease. There was a significant correlation between ET-1 levels and FENO in the three groups of asthmatics and between ET-1 and blood eosinophil counts in the group of patients with unstable asthma. Measurements of ET-1 in EBC may provide another useful diagnostic tool for detecting and monitoring inflammation in patients with asthma.

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.

Endothelin-1 in exhaled breath condensate of allergic asthma patients with exercise-induced bronchoconstriction

Background

Exercise-induced bronchoconstriction (EIB) is a highly prevalent condition, whose pathophysiology is not well understood. Endothelins are proinflammatory, profibrotic, broncho- and vasoconstrictive peptides which play an important role in the development of airway inflammation and remodeling in asthma. The aim of the study was to evaluate the changes in endothelin-1 levels in exhaled breath condensate following intensive exercise in asthmatic patients.

Methods

The study was conducted in a group of 19 asthmatic patients (11 with EIB, 8 without EIB) and 7 healthy volunteers. Changes induced by intensive exercise in the concentrations of endothelin-1 (ET-1) in exhaled breath condensate (EBC) during 24 hours after an exercise challenge test were determined. Moreover, the possible correlations of these measurements with the results of other tests commonly associated with asthma and with the changes of airway inflammation after exercise were observed.

Results

In asthmatic patients with EIB a statistically significant increase in the concentration of ET-1 in EBC collected between 10 minutes and 6 hours after an exercise test was observed. The concentration of ET-1 had returned to its initial level 24 hours after exercise. No effects of the exercise test on changes in the concentrations of ET-1 in EBC in either asthmatic patients without EIB or healthy volunteers were observed. A statistically significant correlation between the maximum increase in ET-1 concentrations in EBC after exercise and either baseline F_ENO and the increase in F_ENO or BHR to histamine 24 hours after exercise in the groups of asthmatics with EIB was revealed.

Conclusion

The release of ET-1 from bronchial epithelium through the influence of many inflammatory cells essential in asthma and interactions with other cytokines, may play an important role in increase of airway inflammation which was observed after postexercise bronchoconstriction in asthmatic patients.

Signaling by ALK5 mediates TGF-β-induced ET-1 expression in endothelial cells: a role for migration and proliferation

Endothelin-1 (ET-1) is a potent endothelial-derived 21-amino-acid vasoconstrictor peptide and its expression is potently regulated by the cytokine transforming growth factor-β (TGF-β). Most cell types contain a TGF-β type I receptor form known as activin receptor-like kinase 5 (ALK5). However, endothelial cells coexpress an additional type I receptor named ALK1. These forms do not constitute redundant receptors with the same function, but they activate different Smad-mediated expression programmes leading to specific endothelial phenotypes. The aim of our study was to characterize the TGF-β-induced pathway leading to ET-1 expression in endothelial cells and the contribution of the TGF-β-mediated enhancement of ET-1 to the regulation of the endothelial cell migration and proliferation capacity. Our experiments indicate that TGF-β induces ET-1 expression preferentially through the ALK5/Smad3 pathway. Specific ALK5 inhibition totally blocked the anti-angiogenic effect of TGF-β. Antagonism of ET receptors partially reverted the effect of TGF-β, indicating that a significant portion of the anti-migratory and anti-proliferative actions of this cytokine is mediated by ET-1 acting in an autocrine manner on endothelial cells.

The role of endothelium-derived mediators in exercise-induced bronchoconstriction

BACKGROUND

Exercise-induced bronchoconstriction (EIB) is a highly prevalent condition whose pathogenesis and effect on airways remain unclear. The aim of the study was to evaluate the changes in endothelial-derived mediators following intensive exercise in asthmatic patients.

METHODS

The study was conducted in a group of 25 asthmatic patients (15 with EIB, 10 without EIB) and 8 healthy volunteers. Changes induced by intensive exercise in the plasma concentrations of endothelin-1 (ET-1), thrombomodulin and soluble E-selectin were determined. Moreover, the possible correlations of these measurements with the results of baseline lung function, bronchial hyperreactivity (BHR), exhaled nitric oxide (F(ENO)), baseline eosinophil cationic protein, peripheral blood eosinophilia and total IgE were investigated.

RESULTS

In the group of asthmatics with EIB, statistically significantly higher baseline concentrations of ET-1 and soluble E-selectin compared with asthmatics with negative exercise test results were revealed. In this group of patients, ET-1, thrombomodulin and soluble E-selectin concentrations significantly increased after exercise. Baseline concentrations of ET-1 as well as an increase in soluble E-selectin concentrations 60 min after exercise showed a statistically significant correlation with baseline eosinophil cationic protein, F(ENO) and BHR. The increase in plasma concentrations of ET-1 15 min after exercise and soluble E-selectin 60 min after exercise showed a statistically significant correlation with the increase in F(ENO) and BHR to histamine 24 h after exercise.

CONCLUSIONS

We suggest that during EIB changes in the function of pulmonary endothelium occur and these changes may influence inflammation of the airway and remodeling in asthmatic patients.

Regulatory peptides modulate adhesion of polymorphonuclear leukocytes to bronchial epithelial cells through regulation of interleukins, ICAM-1 and NF-kappaB/IkappaB

A complex network of regulatory neuropeptides controls airway inflammation reaction, in which airway epithelial cells adhering to and activating leukocytes is a critical step. To study the effect of intrapulmonary regulatory peptides on adhesion of polymorphonuclear leukocytes (PMNs) to bronchial epithelial cells (BECs) and its mechanism, several regulatory peptides including vasoactive intestinal peptide (VIP), epidermal growth factor (EGF), endothelin-1 (ET-1) and calcitonin gene-related peptide (CGRP), were investigated. The results demonstrated that VIP and EGF showed inhibitory effects both on the secretion of IL-1, IL-8 and the adhesion of PMNs to BECs, whereas ET-1 and CGRP had the opposite effect. Anti-intercellular adhesion molecule-1 (ICAM-1) antibody could block the adhesion of PMNs to ozone-stressed BECs. Using immunocytochemistry and reverse transcription-polymerase chain reaction (RT-PCR), it was shown that VIP and EGF down-regulated the expression of ICAM-1 in BECs, while ET-1 and CGRP up-regulated ICAM-1 expression. NF-kappaB inhibitor MG132 blocked ICAM-1 expression induced by ET-1 and CGRP. Furthermore, in electric mobility shift assay (EMSA), VIP and EGF restrained the binding activity of NF-kappaB to the NF-kappaB binding site within the ICAM-1 promoter in ozone-stressed BECs, while CGRP and ET-1 promoted this binding activity. IkappaB degradation was consistent with NF-kappaB activation. These observations indicate that VIP and EGF inhibit inflammation, while ET-1 and CGRP enhance the inflammation reaction.

Airway remodeling in asthma

PURPOSE OF REVIEW

This overview summarizes some the more recent studies of remodeling in patients with asthma, studies using animal models to study the interaction of cell types and mediators, and studies using in vitro models to assess the effects of mitogenic stimuli, including mechanical strain, on mesenchymal cells and extracellular matrix proteins. The aim is to demonstrate how the term remodeling is becoming increasingly less specific as reductionism is applied to this field of study.

RECENT FINDINGS

Specific areas of recent interest include plasticity of airway smooth muscle and fibroblast phenotype; the role of the extracellular matrix and its relation to the function of the airway smooth muscle and the mechanical properties of the airway wall; mitogenic stimuli arising from damaged epithelium, fibroblasts, smooth muscle cells, mast cells, eosinophils, and mechanical stress; extracellular and intracellular signaling in fibroblasts and smooth muscle cells; and therapeutic targets among the many pathways of remodeling-pathways that may be distinct from those involved in inflammation. The potential functional consequences of some of these findings call into question the role of remodeling. In some respects, it may represent a continuum from inflammation to scarring, but it may also be a protective response to altered airway mechanics caused by ongoing tissue damage or by abnormal airway structure present from early in life.

SUMMARY

The diverse areas of research in this field are increasingly making the term remodeling as useful (or not) as the word asthma, because both can be used to describe simultaneously a large number of processes that may or may not be related to each other.