Augmented epithelial endothelin-1 expression in refractory asthma

doi:10.1016/j.jaci.2007.09.023

Journal of Allergy and Clinical Immunology

Volume 120, Issue 6, December 2007, Pages 1301-1307

https://doi.org/10.1016/j.jaci.2007.09.023 Get rights and content

Background

Airway remodeling in patients with severe steroid-refractory asthma might result from a reduced ability of steroid therapy to limit the transcription of remodeling factors by the bronchial epithelium.

Objective

We sought to compare the levels of transcripts encoding remodeling factors in bronchial epithelium of healthy volunteers and of asthmatic patients with either steroid-sensitive or steroid-refractory disease and to correlate these levels with hallmarks of airway remodeling.

Methods

By means of real-time quantitative PCR, we assessed the levels of 14 transcripts encoding remodeling factors, matrix metalolproteinases, and extracellular matrix proteins in laser-capture microdissected bronchial epithelium of healthy volunteers, patients with mild steroid-untreated asthma, and patients with steroid-sensitive and steroid-refractory asthma (n = 8-10 in each group). Histologic features of airway remodeling and endothelin-1 (EDN1) immunolocalization were determined by using frozen specimens.

Results

Patients with steroid-refractory asthma had greater levels of EDN1 transcripts (4.1-fold increase, P = .026) and protein (P = .0009) in their bronchial epithelium compared with patients with steroid-sensitive asthma. EDN1 mRNA levels and protein expression in asthmatic patients were negatively correlated with prebronchodilator and postbronchodilator FEV₁ value (r² ≥ 0.193, P ≤ .03), and they were positively related to airway smooth muscle areas (r² = 0.253, P = .01 and r² = 0.281, P = .005 for EDN1 mRNA and protein expression, respectively).

Conclusion

Increased EDN1 synthesis by the bronchial epithelium characterizes severe refractory asthma and correlates with airway remodeling and airflow obstruction.

Clinical implications

Targeting EDN1 might represent a novel therapeutic strategy for severe steroid-refractory asthma.

Section snippets

Subjects

Ten healthy volunteers, 10 patients with mild steroid-untreated asthma, and 18 patients with severe steroid-treated asthma fulfilling National Institute of Health criteria¹⁹ were recruited (see Table E1 in the Online Repository at www.jacionline.org). All subjects had never smoked. A flow-volume curve was performed in all subjects, and FEV₁ was assessed before and after the inhalation of 400 μg of salbutamol. All subjects provided written informed consent, and the protocol was approved by the

Transcript levels in microdissected bronchial epithelium

Using quantitative real-time PCR, we found detectable amounts of the transcripts encoding all the factors tested (Table I; Table E3 in the Online Repository at www.jacionline.org). The highest expression was found for tenascin C, TGF-α, MMP-2, and fibronectin 1 (values of cycle threshold ranging from 22.6 to 25.6, Table I). Exemplary original quantitative real-time PCR amplification plots are shown in Fig E2 of the Online Repository at www.jacionline.org.

By using the correction for multiple

Discussion

Using laser-capture microdissection coupled to quantitative real-time PCR, we demonstrated that the levels of IL-8/CXCL8 and EDN1 mRNA were significantly augmented in the bronchial epithelium from patients with refractory asthma. These subjects' FEV₁ values failed to improve to greater than 70% of predicted value and less than 15% from baseline value after 14 days of treatment with 0.75 mg/kg/d oral prednisone, and they maintain severe airflow obstruction despite long-term treatment with high

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Recent examples include thymic stromal lymphopoietin, an epithelial-derived cytokine expressed in the asthmatic airway, which has been shown to activate dendritic cells, promote Th2 responses, and activate mast cells.61–63 Endothelin-1 is also increased in airway epithelial biopsies in patients with severe asthma and in particular in patients with steroid-resistant asthma.64 Particulate matter has also been shown to induce the release of proinflammatory mediators and induce cycloxygenase-2 expression in human airway epithelial cells.65
There has been an increased understanding, over the past 2 decades, that asthma is a chronic, immunologically mediated condition with a disturbance of the normal airway repair mechanism, which results in inflammatory changes and airway remodeling. The airway inflammation and remodeling together likely explain the clinical manifestations of asthma. The mechanisms by which the external environmental cues, together with the complex genetic actions, propagate the inflammatory process that characterize asthma are beginning to be understood. There is also an evolving awareness of the active participation of structural elements, such as the airway epithelium, airway smooth muscle, and endothelium, in this process. In tandem with this has come the realization that inflammatory cells respond in a coordinated, albeit dysfunctional manner, via an array of complex signaling pathways that facilitate communication between these cells; these structural elements within the lung and the bone marrow serve as reservoirs for and the source of inflammatory cells and their precursors. Although often viewed as separate mechanistic entities, so-called innate and acquired immunity often overlap in the propagation of the asthmatic response. This review examines the newer information on the pathophysiologic characteristics of asthma and focuses on papers published over the past 3 years that have helped to improve current levels of understanding.
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: Supported in part by the “Agence Nationale de la Recherche,” Paris, France (grant no. 0012405). Sophie Pégorier was funded by the “Chancellerie des Universités de Paris en Sorbonne,” Paris, France.

: Disclosure of potential conflict of interest: The authors have declared that they have no conflict of interest.

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Mechanisms of asthma and allergic inflammationAugmented epithelial endothelin-1 expression in refractory asthma

Background

Objective

Methods

Results

Conclusion

Clinical implications

Section snippets

Subjects

Transcript levels in microdissected bronchial epithelium

Discussion

J Allergy Clin Immunol

J Allergy Clin Immunol

J Allergy Clin Immunol

Curr Opin Pharmacol

J Allergy Clin Immunol

J Allergy Clin Immunol

Pulm Pharmacol Ther

Eur J Pharmacol

J Allergy Clin Immunol

J Allergy Clin Immunol

J Allergy Clin Immunol

Biochem Biophys Res Commun

Int J Biochem Cell Biol

Peptides

Int J Immunopharmacol

J Allergy Clin Immunol

J Allergy Clin Immunol

J Allergy Clin Immunol

Proceeding of the ATS workshop on refractory asthma

Am J Respir Crit Care Med

Asthma. From bronchoconstriction to airways inflammation and remodeling

Am J Respir Crit Care Med

Severe asthma in adults

Am J Respir Crit Care Med

Mechanisms of asthma and allergic inflammation
Augmented epithelial endothelin-1 expression in refractory asthma