Background Acute exacerbations of chronic inflammatory lung diseases, such as chronic obstructive pulmonary disease (COPD), are frequently associated with rhinovirus (RV) infections. Despite these... Show moreBackground Acute exacerbations of chronic inflammatory lung diseases, such as chronic obstructive pulmonary disease (COPD), are frequently associated with rhinovirus (RV) infections. Despite these associations, the pathogenesis of virus-induced exacerbations is incompletely understood. We aimed to investigate effects of cigarette smoke (CS), a primary risk factor for COPD, on RV infection in airway epithelium and identify novel mechanisms related to these effects. Methods Primary bronchial epithelial cells (PBEC) from COPD patients and controls were differentiated by culture at the air-liquid interface (ALI) and exposed to CS and RV-A16. Bulk RNA sequencing was performed using samples collected at 6 and 24 h post infection (hpi), and viral load, mediator and l-lactate levels were measured at 6, 24 and 48hpi. To further delineate the effect of CS on RV-A16 infection, we performed growth differentiation factor 15 (GDF15) knockdown, l-lactate and interferon pre-treatment in ALI-PBEC. We performed deconvolution analysis to predict changes in the cell composition of ALI-PBEC after the various exposures. Finally, we compared transcriptional responses of ALI-PBEC to those in nasal epithelium after human RV-A16 challenge. Results CS exposure impaired antiviral responses at 6hpi and increased viral replication at 24 and 48hpi in ALI-PBEC. At 24hpi, CS exposure enhanced expression of RV-A16-induced epithelial interferons, inflammation-related genes and CXCL8. CS exposure increased expression of oxidative stress-related genes, of GDF15, and decreased mitochondrial membrane potential. GDF15 knockdown experiments suggested involvement of this pathway in the CS-induced increase in viral replication. Expression of glycolysis-related genes and l-lactate production were increased by CS exposure, and was demonstrated to contribute to higher viral replication. No major differences were demonstrated between COPD and non-COPD-derived cultures. However, cellular deconvolution analysis predicted higher secretory cells in COPD-derived cultures at baseline. Conclusion Altogether, our findings demonstrate that CS exposure leads to higher viral infection in human bronchial epithelium by altering not only interferon responses, but likely also through a switch to glycolysis, and via GDF15related pathways. Show less
The research described in this thesis focuses on the responses of lung epithelial cells lining the airways and alveoli. In the study, the effects of viruses that cause lung infections on these... Show moreThe research described in this thesis focuses on the responses of lung epithelial cells lining the airways and alveoli. In the study, the effects of viruses that cause lung infections on these epithelial cells were mapped in detail. Combinations with exposure to cigarette smoke were also included. To do this, epithelial cells obtained from lung tissue were cultured in the lab and exposed to rhinovirus, a common cold virus, and to SARS-CoV-2, which causes COVID-19. Exposure of the epithelial cells to these viruses induces very specific reactions in the airway epithelium. These can be further affected by cigarette smoke. The results of our research have taught us more about the processes specifically involved in the different responses of the epithelium, and how external factors such as cigarette smoke influence these responses. For example, we now better understand how cigarette smoke leads to a higher infection rate of rhinovirus, and it has become clear that the response of the airway epithelium to SARS-CoV-2 differs from the response to other coronaviruses. Our findings are therefore important for a better understanding of the role of viral infections in patients with chronic obstructive pulmonary disease (COPD), and for understanding what makes SARS-CoV-2 a unique virus. Show less
Exposure to cigarette smoke (CS) is the primary risk factor for developing chronic obstructive pulmonary disease. The impact of CS exposure on the molecular mechanisms involved in mitochondrial... Show moreExposure to cigarette smoke (CS) is the primary risk factor for developing chronic obstructive pulmonary disease. The impact of CS exposure on the molecular mechanisms involved in mitochondrial quality control in airway epithelial cells is incompletely understood. Undifferentiated or differentiated primary bronchial epithelial cells were acutely/chronically exposed to whole CS (WCS) or CS extract (CSE) in submerged or air-liquid interface conditions. Abundance of key regulators controlling mitochondrial biogenesis, mitophagy and mitochondrial dynamics was assessed. Acute exposure to WCS or CSE increased the abundance of components of autophagy and receptor-mediated mitophagy in all models. Although mitochondrial content and dynamics appeared to be unaltered in response to CS, changes in both the molecular control of mitochondrial biogenesis and a shift toward an increased glycolytic metabolism were observed in particular in differentiated cultures. These alterations persisted, at least in part, after chronic exposure to WCS during differentiation and upon subsequent discontinuation of WCS exposure. In conclusion, smoke exposure alters the regulation of mitochondrial metabolism in airway epithelial cells, but observed alterations may differ between various culture models used. Show less
Vitamin D plays an active role in the modulation of innate and adaptive immune responses as well as in the protection against respiratory pathogens, e.g. by increasing expression of the... Show moreVitamin D plays an active role in the modulation of innate and adaptive immune responses as well as in the protection against respiratory pathogens, e.g. by increasing expression of the antimicrobial peptide hCAP18/LL-37. The main aim of this thesis was to elucidate the role of inflammation on the protective effects of vitamin D on respiratory host defense responses in chronic inflammatory lung diseases such as chronic obstructive pulmonary disease (COPD). Airway epithelial host defense responses in COPD patients are defective and these patients are therefore more susceptible to respiratory infections. In this thesis we have shown that exposure to cigarette smoke, a main risk factor for COPD, reduced expression of certain host defense mediators by affecting end-stage airway epithelial differentiation and might explains why COPD patients are more susceptible to respiratory infections. We have further demonstrated in the studies presented in this thesis that certain airway inflammatory mediators could possibly interfere with vitamin D metabolism by promoting expression of vitamin D degrading enzyme CYP24A1, thereby reducing local levels of vitamin D and accompanying protective antimicrobial and anti-inflammatory actions. These new insights may yield possible new strategies to target CYP24A1 that enhance local levels and signaling of vitamin D to increase protection against exacerbations in COPD patients. Show less
The studies presented in this thesis were aimed at developing and using in vitro models that could benefit research towards understanding asthma and COPD. We used an in vitro model... Show moreThe studies presented in this thesis were aimed at developing and using in vitro models that could benefit research towards understanding asthma and COPD. We used an in vitro model representing a Th2-high gene signature and studied how this gene signature may be affected by external factors such as cigarette smoke or drugs. Using these in vitro models may help to predict clinical outcomes, although they will require extensive validation. We also investigated the possibility of using primary human airway epithelial cells to model bacterial and viral exacerbations. Whereas this model is currently still under investigation, it could be particularly useful to study possible biomarkers of exacerbations and how these may be affected by external factors. Additionally, we also developed a new method to expand and differentiate mouse tracheal epithelial cells in vitro. Overall, studying airway epithelial cells may provide important clues for understanding disease pathogenesis, lead to identification of new treatment targets, and may provide important biomarkers. Using airway epithelial cells and their derived biomarkers could significantly improve our understanding in disease phenotypes of asthma and COPD. Additionally, with increasing knowledge of the disease phenotypes, we could better address the unmet need in treatment of asthma and COPD. Show less
