Cigarette smoke impairs basal cell mediated epithelial wound repair and induces expression of the antimicrobial protein RNase 7 via oxidative stress

Abstract

Introduction: Basal cells (BCs) are involved in airway epithelial repair and contribute to innate immunity through production of the antimicrobial protein RNase 7. Interactions of cigarette smoke (CS), wound repair and innate immunity by BCs are largely unknown. Aim: To assess the effect of CS exposure on epithelial wound repair, the role of BCs, and RNase 7 expression in an in vitro airway epithelial injury model. Methods: Differentiated primary bronchial epithelial cells (PBEC) cultured at the air-liquid interface were mechanically injured and exposed to CS or air. Wound closure was measured by live imaging. p63 + BCs were studied by confocal microscopy, and expression of RNASE7 mRNA was assessed by qPCR. The role of oxidative stress was examined using the anti-oxidant N-acetylcysteine (NAC). Results: CS inhibited wound repair in PBEC during the first 6 hours, coinciding with impaired migration of p63 + cells at the wound edge. At later time points wound closure was restored to levels comparable to air controls. Mechanical injury and CS exposure synergistically induced RNASE7 expression. NAC partially prevented the CS-induced inhibition of wound repair and reduced RNASE7 expression. Conclusion: Our data suggest that CS-induced oxidative stress delays epithelial repair by impairing migration of BCs into the wound area, whereas RNase 7 expression is increased. These alterations in BC function induced by CS might influence repair of injured airway epithelium in smokers and might contribute to the development of inflammatory lung diseases, such as COPD. This study was supported by an unrestricted research grant from Galapagos NV.