Enhanced Induction of Epithelial-Derived IL-17C Following Bacteria and Rhinovirus Exposure
Date
2019-05-15
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Up to 80% of Chronic Obstructive Pulmonary Disease (COPD) exacerbations are associated with bacterial and/or viral pathogens, with bacteria-virus co-infections detected in up to 25% of exacerbations. These co-infections are associated with increased symptoms, increased systemic inflammation, longer hospital stays, and increased risk of hospital re-admission. Human rhinovirus (HRV) is the most common viral pathogens detected, while non-typeable Haemophilus influenzae (NTHI) and Pseudomonas aeruginosa (PAO) are among the most common bacterial pathogens identified. The airway epithelium is the first line of defence against these pathogens and responds by releasing proinflammatory cytokines and anti-microbial peptides. Interleukin (IL)-17C is a novel pro-inflammatory cytokine that is typically released from epithelial cells in response to bacteria, viral, or fungal pathogens, and in response to pro-inflammatory cytokines such as TNFα and IL-1β. In this thesis, we performed the first study to assess the involvement and functional role of IL-17C in bacteria-rhinovirus co-infections in human bronchial epithelial cells (HBECs). Bacteria-rhinovirus co-exposure for 24 hours induced significant, and synergistic, IL-17C gene expression and protein release. Synergistic IL-17C release was dependent on viral replication recognition sensors, RIG-I and MDA5, as well as NF-κB and p38 signalling. In an autocrine/paracrine manner, IL-17C acted on the airway epithelium to induce CXCL1, CXCL2, TFRC, and NFKBIZ gene expression, to induce CXCL1 protein release, and to promote HBEC-induced neutrophil recruitment. To assess how IL-17C is involved in the clinical context of COPD, HBECs were obtained via bronchial brushings from non-smokers, smokers with normal lung function, and patients with physician-diagnosed COPD and these cells were exposed to NTHI and HRV-1A concurrently. Interestingly, in response to concurrent NTHI and HRV-1A exposure, HBECs from COPD patients released significantly more IL-17C than cells from either non-smokers or healthy smokers, and HBECs from healthy smokers released significantly less IL-17C than non-smokers. Further, acute cigarette smoke extract exposure significantly reduced microbial-induced IL-17C release from cells from normal subjects. Using a morphologically-relevant well-differentiated HBEC model, IL-17C was predominantly released basolaterally, from apical cells, in response to HRV in a dose-, time-, and replication-dependent manner. High doses of NTHI could also induce basolateral IL-17C, however synergy was no longer achieved with NTHI+HRV-1A co-infections. Similar to monolayer culture, IL-17C acted on basal cells to induce significant basolateral release of CXCL1, providing physiological relevance for subsequent neutrophil recruitment. These results suggest that IL-17C acts to induce CXCL1 release and promote neutrophil recruitment to the site of bacteria or rhinovirus respiratory infections, however, this response is exaggerated in epithelial cells from COPD patients.
Description
Keywords
rhinovirus, bacteria, lung infections, COPD, neutrophil chemotaxis, IL-17C, airway epithelium, cigarette smoke, air-liquid interface
Citation
Jamieson, K. C. (2019). Enhanced Induction of Epithelial-Derived IL-17C Following Bacteria and Rhinovirus Exposure (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.