Airway Epithelial miRNA Expression Is Altered in Asthma

Abstract

Rationale: Changes in airway epithelial cell differentiation, driven in part by IL-13, are important in asthma. Micro-RNAs (miRNAs) regulate cell differentiation in many systems and could contribute to epithelial abnormalities in asthma. Objectives: To determine whether airway epithelial miRNA expression is altered in asthma and identify IL-13-regulated miRNAs. Methods:We used miRNA microarrays to analyze bronchial epithelial brushings from 16 steroid-naive subjects with asthma before and after inhaled corticosteroids, 19 steroid-using subjects with asthma, and 12 healthy control subjects, and the effects of IL-13 and corticosteroids on cultured bronchial epithelial cells. We used quantitative polymerase chain reaction to confirm selected microarray results. Measurements and Main Results: Most (12 of 16) steroid-naive subjects with asthma had a markedly abnormal pattern of bronchial epithelial miRNA expression by microarray analysis. Compared with control subjects, 217 miRNAs were differentially expressed in steroid-naive subjects with asthma and 200 in steroid-using subjects with asthma (false discovery rate , 0.05). Treatment with inhaled corticosteroids had modest effects on miRNA expression in steroid-naive asthma, inducing a statistically significant (false discovery rate , 0.05) change for only nine miRNAs. qPCR analysis confirmed differential expression of 22 miRNAs that were highly differentially expressed by microarrays. IL-13 stimulation recapitulated changes in many differentially expressed miRNAs, including four members of the miR-34/ 449 family, and these changes in miR-34/449 family members were resistant to corticosteroids. Conclusions: Dramatic alterations of airway epithelial cell miRNA levels are a common feature of asthma. These alterations are only modestly corrected by inhaled corticosteroids. IL-13 effects may account for some of these alterations, including repression of miR-34/449 family members that have established roles in airway epithelial cell differentiation. Clinical trial registered with www.clinicaltrials.gov (NCT 00595153).Keywords: miRNA; asthma; airway epithelium Asthma is an inflammatory condition of the lung characterized by episodic airway obstruction and remodeling of airway tissues (1). The airway epithelium is increasingly recognized as an important participant in asthma pathophysiology (2, 3). Airway epithelial cells produce mucus, which is a major contributor to airway obstruction in fatal asthma (4), and even patients with stable mild and moderate asthma have increased epithelial mucin stores (5). Previous human, animal model, and cell culture studies demonstrate that the Th2 cytokine IL-13 is a critical inducer of airway epithelial abnormalities in asthma (6-8). IL-13 stimulation of epithelial cells leads to an increase in the number of mucous cells (mucous metaplasia) and a decrease in the number of ciliated cells (9). IL-13 stimulation of airway epithelial cells activates signal transduction and transcription factor 6, leading to changes in expression of mRNAs that...

Let-7a is differentially expressed in bronchial biopsies of patients with severe asthma

“…Pathway analysis of differentially expressed miRNAs belonged to JAK-STAT signaling, cytokine network, and cytokine and inflammatory response 13 . Let-7a was also found to be reduced in the airway epithelial cells 12 and serum 15 of asthma patients. Thus, reduced expression of let-7a in bronchial biopsies from patients with severe asthma is consistent with the findings of other studies 3,[10][11][12][13][14][15]19,25 .…”

“…However, the data on miRNA expression in the lungs of human subjects with asthma are still scarce. Several miRNAs, such as let7a, miR-21, and miR-223, have been shown to have a role in airway inflammation, T H 1/T H 2 polarization, and eosinophil development either directly or indirectly repress the translation of several crucial factors, and were shown to be differentially expressed in asthma 3,4,[10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] . In the present study we analyzed the expression of three miRNAs (let-7a, miR-21, and miR-223) in bronchial biopsy samples from patients with mild and severe asthma and non-asthmatic controls.…”

“…The variability in treatment response is based on large asthma clinical heterogeneity, and understanding the pattern of airway inflammation and molecular factors regulating those processes could be helpful in defining asthma endotypes and understanding why therapy is not effective in all patients 6 . MicroRNAs (miRNAs), 19-25 nucleotides long non-coding small RNAs involved in regulation of gene expression through a process known as RNA interference 729 , may play a role in orchestrating the phenotypic programming of immune and airway epithelial cells to enhance the production of cytokines and other mediators that result in the inflammation that characterizes asthma 3,4,[10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] . Therefore, miRNAs may contribute to asthma pathology.…”

Subtypes of Asthma Defined by Epithelial Cell Expression of Messenger RNA and MicroRNA

“…However, one might also ask whether these miRNAs can serve as biomarkers of asthma endotypes. Using a similar approach to that which we employed for assessment of mRNA expression in airway epithelial cells, we performed companion experiments with bronchial epithelial cells in vitro and found that IL-13 had significant effects on bronchial epithelial miRNA expression and that several of these changes recapitulated the differences between asthma and health that we observed in our human studies (33). One finding that we have focused on in subsequent work is consistent repression of four members of the miR-34/449 family (miR-34c-5p, miR34c-5p, miR-449a, and miR-449b-5p) both in vivo in asthma and in vitro by IL-13.…”

“…More recently we have observed that microRNAs (miRNAs) are also highly differentially expressed in the airway epithelium of subjects with asthma as compared with healthy control subjects (33). miRNAs are approximately 22-nucleotide RNAs that promote mRNA degradation (34) or inhibit translation (35), by binding with at least partial complementarity to the 39 untranslated region of target mRNAs.…”