Up-regulation of Notch signaling and cell-differentiation inhibitory transcription factors in the lower airways of stable COPD patients

Abstract

Abstract Background: Notch signalling is involved in the prevention of cell differentiation and of cell fate in various organs, including the lung. Objective: To determine transcriptomic and protein expression of Notch receptors, its ligands and related transcription factors in stable COPD. Methods: The expression and localization of Notch receptors, its ligands and related transcription factors were measured in bronchial biopsies of stable mild/moderate (MCOPD) (n=18), severe/very severe (SCOPD) (n=16), COPD, control smokers (CS) (n=13) and control non-smokers (CNS) (n=11), in lung parenchyma of MCOPD (n=13), CS (n=10) and CNS (n=10) using immunohistochemistry, ELISA tests and transcriptome analysis. In “in vitro” experiments Notch pathway was analysed after LPS and H2O2 stimulation of 16HBE cells. Main Results: In bronchial biopsies Notch4 and HES7 significantly increased in the lamina propria of SCOPD compared to MCOPD, CS and CNS. In peripheral lung bronchiolar epithelium Notch1 significantly increased in MCOPD and CS compared to CNS. In alveolar macrophages Notch2 and DLL4 significantly increased in CS compared to CNS. ELISA tests of lung parenchyma homogenates showed significantly increased levels of Notch2 in MCOPD compared to CS and CNS. Transcriptomic data from bronchial rings showed increased DLL1 mRNA levels in CS compared to CNS. In the lung parenchyma DLL4 and HES1 mRNA levels were increased in MCOPD and CS compared to CNS. In vitro stimulation of 16HBE cells with LPS induced a significant increase in DLL4, Notch2, HES1 and HES7 at 4h after challenge. H2O2 stimulation up-regulated significantly HES1 and HES7 at 4h and 24h after challenge. Conclusion: These data show an increased expression of the Notch pathway in the lung of stable COPD. These alterations may play a role in impairing the regenerative-reparative responses of the diseased bronchioles and lung parenchyma.