Airway Mucosal Host Defense Is Key to Genomic Regulation of Cystic Fibrosis Lung Disease Severity.

RATIONALE: The severity of cystic fibrosis (CF) lung disease varies widely, even for Phe508del homozygotes. Heritability studies show that more than 50% of the variability reflects non-cystic fibrosis transmembrane conductance regulator (CFTR) genetic variation; however, the full extent of the pertinent genetic variation is not known. OBJECTIVES: We sought to identify novel CF disease-modifying mechanisms using an integrated approach based on analyzing "in vivo" CF airway epithelial gene expression complemented with genome-wide association study (GWAS) data. METHODS: Nasal mucosal RNA from 134 patients with CF was used for RNA sequencing. We tested for associations of transcriptomic (gene expression) data with a quantitative phenotype of CF lung disease severity. Pathway analysis of CF GWAS data (n = 5,659 patients) was performed to identify novel pathways and assess the concordance of genomic and transcriptomic data. Association of gene expression with previously identified CF GWAS risk alleles was also tested. MEASUREMENTS AND MAIN RESULTS: Significant evidence of heritable gene expression was identified. Gene expression pathways relevant to airway mucosal host defense were significantly associated with CF lung disease severity, including viral infection, inflammation/inflammatory signaling, lipid metabolism, apoptosis, ion transport, Phe508del CFTR processing, and innate immune responses, including HLA (human leukocyte antigen) genes. Ion transport and CFTR processing pathways, as well as HLA genes, were identified across differential gene expression and GWAS signals. CONCLUSIONS: Transcriptomic analyses of CF airway epithelia, coupled to genomic (GWAS) analyses, highlight the role of heritable host defense variation in determining the pathophysiology of CF lung disease. The identification of these pathways provides opportunities to pursue targeted interventions to improve CF lung health.

Prolonged inflammatory response to acute Pseudomonas challenge in interleukin-10 knockout mice.

Cystic fibrosis (CF) lung disease is characterized by a neutrophilic infiltrate that is excessive relative to the burden of infection. Decreased interleukin-10 in CF airways may impair proper termination of inflammation, leading to persistence of neutrophils after acute infections have been cleared. This could explain reports of lung inflammation in the absence of bacteria in infants with CF. We evaluated the kinetics of inflammation after transient Pseudomonas aeruginosa challenge in IL-10 knockout (KO) and wild-type (WT) mice. Both types of mice cleared the infection by Day 6 (p > or = 0.29). However, IL-10 KO mice had more neutrophils in bronchoalveolar lavage fluid than did WT mice on Days 4 (p < 0.0001), 6 (p < 0.0001), and 8 (p = 0.042). IL-10 KO mice had high concentrations of proinflammatory cytokines in BAL on Days 2 and 4, with some cytokines detectable on Days 6 and 8, whereas cytokines in BAL from WT mice were greatest on Day 2 and undetectable by Day 4. Moreover, IL-10 KO mice failed to regenerate IkappaBalpha once degraded and subsequently had prolonged activation of NF-kappaB. These data suggest that IL-10 deficiency contributes to prolonged inflammatory responses early in CF, when infection may be transient.

Effect of ibuprofen on neutrophil migration in vivo in cystic fibrosis and healthy subjects.

Long-term treatment with ibuprofen twice daily, at doses that achieve peak plasma concentration (Cmax) >50 microg/ml, slows progression of lung disease in patients with cystic fibrosis (CF). Previous data suggest that Cmax >50 microg/ml is associated with a reduction in neutrophil (PMN) migration into the lung and that lower concentrations are associated with an increase in PMN migration. To estimate the threshold concentration at which ibuprofen is associated with a decrease in PMN migration in vivo, we measured the PMN content of oral mucosal washes in 35 healthy (age 19-40 years) and 16 CF (age 18-32 years) subjects who took ibuprofen twice daily for 10 days in doses that achieved Cmax 8 to 90 microg/ml. Cmax >50 microg/ml was associated with a 31 +/- 7% (mean +/- S.E.M.) reduction in PMNs in CF (n = 11, p < 0.001) and 25 +/- 6% reduction in PMNs in healthy subjects (n = 16, p < 0.001). Increasing concentrations above 50 microg/ml was not associated with a greater decrease in PMNs. The reduction in PMN migration was consistently present 12 h after a dose, but not after 24 h. Cmax <50 microg/ml was associated with an increase in PMNs of approximately 40%. These results suggest that Cmax >50 microg/ml and twice daily dosing of ibuprofen are required to decrease PMN migration, and reinforce the current recommendation that pharmacokinetics should be performed in CF patients prescribed ibuprofen.