Reduced Interleukin-8 Production by Cystic Fibrosis Airway Epithelial Cells

Abstract

The acquisition of Pseudomonas aeruginosa in the airways of patients with cystic fibrosis (CF) is the initial event leading to bronchiectasis and lung disease. Although the host factors that permit initial airway colonization are largely unknown, recent studies suggest that secretion of interleukin (IL)-8 by airway epithelia and local recruitment of neutrophils is the final pathway in a pulmonary cytokine network. To determine whether differences in cytokine production exist between normal and CF airway epithelia, secretion of immunoreactive IL-8 and IL-10 as well as specific messenger RNA (mRNA) abundance were compared in airway epithelia expressing normal and mutant CF transmembrane regulator. After induction with IL-1beta, a CF airway cell line engineered to express the wild-type CF gene (CFT1-LCFSN) secreted significantly more immunoreactive IL-8 than did its isogenic parent that expressed the mutant CF gene (CFT1) or an isogenic vector control line (CFT1-LC3). Further studies with the three related cell lines demonstrated that expression of CFT1-LCFSN was associated with a significant increase in uninduced secretion of immunoreactive IL-8 as well as a 10- to 20-fold increase in IL-8 mRNA abundance when compared with the isogenic lines expressing the mutant gene. IL-1beta induction and intracellular accumulation of IL-8 appeared to be unaffected by CF genotype. These studies suggest that IL-8 secretion by CF airway epithelial cells is defective and may contribute to Pseudomonas persistence in the CF airway. Further studies are needed to confirm this difference in other cell lines and determine the linkage between IL-8 production and CF gene expression.

Does the ΔF508-CFTR mutation induce a proinflammatory response in human airway epithelial cells?

“…We report that P. aeruginosa elicited a more robust increase in cytokine and chemokine expression (e.g., IL-8, CXCL1, CXCL2, and TNF-␣) in CFBE-wt-CFTR cells compared with CFBE-⌬F508-CFTR cells. These data add to a growing body of evidence revealing that the inflammatory response of human airway epithelial cells expressing wt-CFTR and ⌬F508-CFTR to P. aeruginosa is model dependent, even when considering matched cell lines and human airway epithelial cells in primary culture (4,6,8,16,18,22,26,28,31,37,39,41). Taken together with other published studies, our data demonstrate that there is no compelling evidence to support the view that mutations in CFTR induce a hyperinflammatory response in human airway epithelial cells in vivo.…”

“…However, even studies on matched cell lines do not produce consistent results. For example, studies on IB3-1 (⌬F508/W1282X) and S9 cells (IB3-1 cells complemented with wt-CFTR) demonstrate that P. aeruginosa elicits a more robust increase in IL-8 production in IB3-1 CF cells than in wt-CFTR-corrected S9 cells (1,10), whereas studies on other matched cell lines reveal that, when challenged with P. aeruginosa, CF cells actually produce less IL-8 than non-CF cells, contrary to the generally accepted view that CF mutations enhance the inflammatory response of airway epithelial cells to P. aeruginosa (16,22,31).…”

“…Although it is generally assumed that CF airway epithelial cells are hyperinflammatory in response to P. aeruginosa compared with non-CF airway epithelial cells, human CF airway cells in culture often fail to show a hyperinflammatory phenotype compared with airway epithelial cells expressing wild-type (wt)-CFTR (16,21,35). Indeed, one-third of published studies reveal that CF airway cells elaborate a more robust increase in IL-8 production than non-CF cells in response to P. aeruginosa (28,37,39,41), one-third report no difference (4,6,8,16,26), and one-third actually report that wt-CFTR cells release more IL-8 than CF cells in response to P. aeruginosa (18,22,31). Moreover, because the lungs during infection with P. aeruginosa contain immune cells that, like airway epithelial cells, produce cytokines and chemokines, it is not possible to determine whether the cytokines and chemokines in vivo originate from immune cells and/or airway epithelial cells.…”

Defective regulatory volume decrease in human cystic fibrosis tracheal cells because of altered regulation of intermediate conductance Ca 2+ -dependent potassium channels

“…The vector control cell line CFT1-LC3 was obtained by transfection of CFT1 cells with a retroviral vector encoding ␤-galactosidase (␤gal), and CFT1-LCFSN was obtained by transfection of CFT1 with wild-type CFTR (13). The three cell lines were grown in Ham's F-12 medium (GIBCO) supplemented with 10 g͞ml insulin (GIBCO), 0.5 g͞ml hydrocortisone (Sigma), 3.75 g͞ml endothelial cell growth supplement (Sigma), 25 ng͞ml epidermal growth factor (Sigma), 3 ϫ 10…”

G551D Cystic Fibrosis Mice Exhibit Abnormal Regulation of Inflammation in Lungs and Macrophages

“…In a mouse CF model, instillation of P. aeruginosa embedded in agar beads results in increased production of inflammatory cytokines in CF animals compared with similarly treated wild-type controls (15). Recent studies have demonstrated that CF epithelia are not responsible for the overexpression of these proinflammatory cytokines (16).…”