Abstract
In COPD, matrix remodeling contributes to airflow limitation. Recent evidence suggests that next to fibroblasts, the process of epithelial-mesenchymal transition can contribute to matrix remodeling. CSE has been shown to induce EMT in lung epithelial cells, but the signaling mechanisms involved are largely unknown and subject of this study. EMT was assessed in A549 and BEAS2B cells stimulated with CSE by qPCR, Western blotting and immunofluorescence for epithelial and mesenchymal markers, as were collagen production, cell adhesion and barrier integrity as functional endpoints. Involvement of TGF-β and HIF1α signaling pathways were investigated. In addition, mouse models were used to examine the effects of CS on hypoxia signaling and of hypoxia per se on mesenchymal expression. CSE induced EMT characteristics in A549 and BEAS2B cells, evidenced by decreased expression of epithelial markers and a concomitant increase in mesenchymal marker expression after CSE exposure. Furthermore cells that underwent EMT showed increased production of collagen, decreased adhesion and disrupted barrier integrity. The induction of EMT was found to be independent of TGF-β signaling. On the contrary, CS was able to induce hypoxic signaling in A549 and BEAS2B cells as well as in mice lung tissue. Importantly, HIF1α knock-down prevented induction of mesenchymal markers, increased collagen production and decreased adhesion after CSE exposure, data that are in line with the observed induction of mesenchymal marker expression by hypoxia in vitro and in vivo. Together these data provide evidence that both bronchial and alveolar epithelial cells undergo a functional phenotypic shift in response to CSE exposure which can contribute to increased collagen deposition in COPD lungs. Moreover, HIF1α signaling appears to play an important role in this process.
Highlights
Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation that is progressive and not fully reversible
To test the effect of cigarette smoke on these markers we first tested the effect of cigarette smoke extract (CSE) on viability of A549 and BEAS2B cells
In this study it is shown that CSE induced epithelial-mesenchymal transition (EMT) in alveolar and bronchial epithelial cells
Summary
Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation that is progressive and not fully reversible. The airflow limitation is often ascribed to remodeling, which consists of airway wall thickening and/or emphysema [1]. The association between remodeling and cigarette smoking, the main risk factor for COPD, has been established in both human and animal models [2,3]. Most of these studies show airway wall thickening based on image analysis. Studies into the molecular changes in extracellular matrix associated with small airway remodeling in COPD and mechanisms involved are few, and mainly focus on collagen, fibronectin and glycosaminoglycan deposition [4,5]. The bronchial and alveolar compartment are mostly considered independent entities we recently showed that the matrix of small airway walls and alveolar walls of COPD patients displays very similar features of remodelling [10]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
