Cystic Fibrosis Transmembrane Conductance Regulator Regulates Epithelial Cell Response to Aspergillus and Resultant Pulmonary Inflammation

Abstract

Rationale: Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) alter epithelial cell (EC) interactions with multiple microbes, such that dysregulated inflammation and injury occur with airway colonization in people with cystic fibrosis (CF). Aspergillus fumigatus frequently colonizes CF airways, but it has been assumed to be an innocent saprophyte; its potential role as a cause of lung disease is controversial. Objectives: To study the interactions between Aspergillus and EC, and the role of the fungus in evoking inflammatory responses. Methods: A. fumigatus expressing green fluorescent protein was developed for in vitro and in vivo models, which used cell lines and mouse tracheal EC. Measurements and Main Results: Fungal spores (conidia) are rapidly ingested by ECs derived from bronchial cell lines and murine tracheas, supporting a role for EC in early airway clearance. Bronchial ECs harboring CFTR mutations (DF508) or deletion demonstrate impaired uptake and killing of conidia, and ECs with CFTR mutation undergo more conidial-induced apoptosis. Germinated (hyphal) forms of the fungus evoke secretion of inflammatory mediators, with CFTR mutation resulting in increased airway levels of macrophage inflammatory protein 2 and KC, and higher lung monocyte chemotactic protein-1. After A. fumigatus inhalation, CFTR 2/2 mice develop exaggerated lymphocytic inflammation, mucin accumulation, and lung injury. Conclusions: Data demonstrate a critical role for CFTR in mediating EC responses to A. fumigatus. Results suggest that the fungus elicits aberrant pulmonary inflammation in the setting of CFTR mutation, supporting the potential role of antifungals to halt progressive CF lung disease.

Newborn Cystic Fibrosis Pigs Have a Blunted Early Response to an Inflammatory Stimulus

“…Consistent with this, work with CF cell lines and cells cultured from the airways of CF mice indicate that CF airway cells are comparatively more sensitive to apoptotic induction by drugs (46,47), fungal spores (48), and cigarette smoke (49). Conversely, Gottlieb and colleagues (50) reported that mutant CFTR confers resistance to a proapoptotic drug.…”

Update in Cystic Fibrosis 2012

“…Studies provide further support for the concept that A. fumigatus may not be an innocent bystander in CF lung disease. Chaudhary and colleagues used a combination of in vitro and in vivo studies to demonstrate that A. fumigatus uptake by CFTR-deficient cells is reduced, but that epithelial cell apoptosis after exposure to A. fumigatus is increased (11). This raises a question concerning whether CFTR plays a role in intracellular uptake of A. fumigatus as previously demonstrated for P. aeruginosa (12).…”

Current Concepts and Controversies in Innate Immunity of Cystic Fibrosis Lung Disease

“…Direct interaction between the CFTR protein and pathogens has been previously suggested, where CFTR serves as a receptor for Salmonella typhi [108] and P. aeruginosa [109,110] when expressed on intestinal or airway epithelial cells, respectively. Moreover, A. fumigatus spores are readily ingested by airway epithelial cells and the uptake and killing of conidia are both impaired in epithelial cells lacking CFTR [111]. The bronchial epithelium has been previously shown to modulate its sensitivity towards microbial recognition by regulating receptor expression levels [112].…”