Inflammasome-Mediated IL-1β Production in Humans with Cystic Fibrosis

Anthony Tang,Mark A. Chilvers,Ashish Sharma,Roger Jen,Aaron F. Hirschfeld,Stuart E. Turvey,Pascal M. Lavoie,David M. Ojcius

doi:10.1371/journal.pone.0037689

Abstract

BackgroundInflammation and infection are major determinants of disease severity and consequently, the quality of life and outcome for patients with cystic fibrosis (CF). Interleukin-1 beta (IL-1β) is a key inflammatory mediator. Secretion of biologically active IL-1β involves inflammasome-mediated processing. Little is known about the contribution of IL-1β and the inflammasomes in CF inflammatory disease. This study examines inflammasome-mediated IL-1β production in CF bronchial epithelial cell lines and human patients with CF.ResultsBronchial epithelial cell lines were found to produce negligible amounts of basal or stimulated IL-1β compared to hematopoeitic cells and they did not significantly upregulate caspase-1 activity upon inflammasome stimulation. In contrast, peripheral blood mononuclear cells (PBMCs) from both CF and healthy control subjects produced large amounts of IL-1β and strongly upregulated caspase-1 activity upon inflammasome stimulation. PBMCs from CF patients and controls displayed similar levels of caspase-1 activation and IL-1β production when stimulated with inflammasome activators. This IL-1β production was dependent on NF-κB activity and could be enhanced by priming with LPS. Finally, chemical inhibition of CFTR activity in control PBMCs and THP-1 cells did not significantly alter IL-1β or IL-8 production in response to P. aeruginosa.ConclusionHematopoeitic cells appear to be the predominant source of inflammasome-induced pro-inflammatory IL-1β in CF. PBMCs derived from CF subjects display preserved inflammasome activation and IL-1β secretion in response to the major CF pathogen Pseudomonas aeruginosa. However, our data do not support the hypothesis that increased IL-1β production in CF subjects is due to an intrinsic increase in NF-κB activity through loss of CFTR function.

Highlights

Cystic fibrosis is an autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), which functions as a chloride ion channel
To determine if airway epithelial cells contribute to the increased Interleukin-1 beta (IL-1b) production in patients with CF, CF and control bronchial epithelial cell lines were stimulated with the inflammasome inducers P. aeruginosa strain PAO1 (PAO1) and LPS followed by adenosine triphosphate (ATP)
IL-1b levels in cell culture supernatants were not greatly increased in either the CF or control cell lines (Fig. 2a–d), a small increase in IL-1b production was detected in NuLi-1 and CuFi-1 cells, but not in S9 and IB3-1 cells, by 24 hours

Summary

Introduction

Cystic fibrosis is an autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), which functions as a chloride ion channel. In CF, airway epithelial cells have been shown to produce an exaggerated pro-inflammatory cytokine response to stimulation [4,5]. It is unclear whether this heightened inflammatory response is intrinsic to cells lacking CFTR or whether it is a result of chronic polymicrobial infection [6,7]. Regardless of this controversy, identifying and targeting relevant inflammatory mediators is a critical step in developing more specific therapeutic approaches to control inflammation and improve health outcomes in CF [8]. This study examines inflammasome-mediated IL-1b production in CF bronchial epithelial cell lines and human patients with CF

Methods

Results

Discussion

Conclusion