Relation of exaggerated cytokine responses of CF airway epithelial cells to PAO1 adherence

Abstract

In many model systems, cystic fibrosis (CF) phenotype airway epithelial cells in culture respond to P. aeruginosa with greater interleukin (IL)-8 and IL-6 secretion than matched controls. In order to test whether this excess inflammatory response results from the reported increased adherence of P. aeruginosa to the CF cells, we compared the inflammatory response of matched pairs of CF and non CF airway epithelial cell lines to the binding of GFP-PAO1, a strain of pseudomonas labeled with green fluorescent protein. There was no clear relation between GFP-PAO1 binding and cytokine production in response to PAO1. Treatment with exogenous aGM1 resulted in greater GFP-PAO1 binding to the normal phenotype compared to CF phenotype cells, but cytokine production remained greater from the CF cell lines. When cells were treated with neuraminidase, PAO1 adherence was equalized between CF and nonCF phenotype cell lines, but IL-8 production in response to inflammatory stimuli was still greater in CF phenotype cells. The polarized cell lines 16HBEo-Sense (normal phenotype) and Antisense (CF phenotype) cells were used to test the effect of disrupting tight junctions, which allows access of PAO1 to basolateral binding sites in both cell lines. IL-8 production increased from CF, but not normal, cells. These data indicate that increased bacterial binding to CF phenotype cells cannot by itself account for excess cytokine production in CF airway epithelial cells, encourage investigation of alternative hypotheses, and signal caution for therapeutic strategies proposed for CF that include disruption of tight junctions in the face of pseudomonas infection.

Sputum Biomarkers of Inflammation in Cystic Fibrosis Lung Disease

“…Defective cytokine production in airway epithelial cells, which are dependent on CFTR for normal secretory function, could explain why the disorders of the inflammatory response in CF seem limited to the respiratory tract (23,29,30,36). Importantly, there is no increase in the frequency or severity of infection outside the respiratory tract, as would be found in patients with neutrophil defects or other primary immune deficiencies.…”

“…There is supportive evidence suggesting a direct linkage between abnormal CFTR and the excessive airway inflammatory response. Inhibition of CFTR production by antisense oligonucleotides or inhibition of CFTR function by overexpression of the regulatory (R) domain of CFTR in epithelial cell lines results in increased activation of NF-B and increased secretion of IL-8 upon stimulation of these cells with proinflammatory stimuli (23,24,36,42). Further studies using a pharmacologic inhibitor of CFTR demonstrate that intact CFTR channel function is necessary for normal regulation of inflammatory cascades in epithelial cells (25).…”

Is cystic fibrosis a TH17 disease?

“…Other investigators have shown that the CF epithelium produces higher levels of the inflammatory cytokines IL-6 and IL-8 in response to P. aeruginosa or specific Toll-like receptor 4 agonists [12]. This pro-inflammatory state is associated with defective phosphorylation of STAT1 and induction of inducible nitric oxide synthase [23,24]. Moreover, although cftr knockout mice do not show chronic colonization with P. aeruginosa, they do show exaggerated inflammatory responses to P. aeruginosa challenge, particularly in terms of the elaboration of the CXC chemokine KC (a murine IL-8 homolog) and IL-6 [25,26].…”

Trimethylangelicin reduces IL-8 transcription and potentiates CFTR function

“…CF affects several organs, with the chronic pulmonary disease being the major cause of reduction of the quality and expectancy of life. The hallmark of CF lung disease is chronic infection sustained by the gram-negative bacterium Pseudomonas aeruginosa and excessive lung inflammation with a huge infiltrate of neutrophils in the bronchial lumen, mainly due to the release of the chemokine interleukin (IL)-8 (2,4,5,11,24,27,36). The identification of novel drugs, to reduce the excessive lung inflammation in CF, is considered a key therapeutic target to circumvent progressive lung tissue deterioration (for review, see Ref.…”