Inflammasome-Mediated IL-1b Production in Humans with Cystic Fibrosis Anthony Tang1, Ashish Sharma2, Roger Jen2, Aaron F. Hirschfeld3, Mark A. Chilvers3, Pascal M. Lavoie2,3, Stuart E. Turvey1,2,3* 1 Department of Microbiology & Immunology, University of British Columbia, Vancouver, British Columbia, Canada, 2 Department of Experimental Medicine, University of British Columbia, Vancouver, British Columbia, Canada, 3 Department of Pediatrics, British Columbia Children’s Hospital and Child & Family Research Institute, Vancouver, British Columbia, Canada Abstract Background: Inflammation 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-1b) is a key inflammatory mediator. Secretion of biologically active IL-1b involves inflammasome-mediated processing. Little is known about the contribution of IL-1b and the inflammasomes in CF inflammatory disease. This study examines inflammasome-mediated IL-1b production in CF bronchial epithelial cell lines and human patients with CF. Results: Bronchial epithelial cell lines were found to produce negligible amounts of basal or stimulated IL-1b 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-1b and strongly upregulated caspase-1 activity upon inflammasome stimulation. PBMCs from CF patients and controls displayed similar levels of caspase-1 activation and IL-1b production when stimulated with inflammasome activators. This IL- 1b production was dependent on NF-kB 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-1b or IL-8 production in response to P. aeruginosa. Conclusion: Hematopoeitic cells appear to be the predominant source of inflammasome-induced pro-inflammatory IL-1b in CF. PBMCs derived from CF subjects display preserved inflammasome activation and IL-1b secretion in response to the major CF pathogen Pseudomonas aeruginosa. However, our data do not support the hypothesis that increased IL-1b production in CF subjects is due to an intrinsic increase in NF-kB activity through loss of CFTR function. Citation: Tang A, Sharma A, Jen R, Hirschfeld AF, Chilvers MA, et al. (2012) Inflammasome-Mediated IL-1b Production in Humans with Cystic Fibrosis. PLoS ONE 7(5): e37689. doi:10.1371/journal.pone.0037689 Editor: David M. Ojcius, University of California Merced, United States of America Received September 26, 2011; Accepted April 24, 2012; Published May 23, 2012 Copyright: 2012 Tang et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by: BC Lung Association (www.bc.lung.ca); Cystic Fibrosis Canada (www.cysticfibrosis.ca); Michael Smith Foundation For Health Research (www.msfhr.org/); Canadian Institutes For Health Research (www.cihr-irsc.gc.ca); and Child & Family Research Institute (www.cfri.ca). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: sturvey@cw.bc.ca 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. CF remains one of the most common lethal genetic diseases in populations of European descent with the current average lifespan of CF patients approximately 40 years of age [1,2]. Recurrent inflammatory pulmonary exacerbation is the primary cause of lung disease progression and ultimately, death in CF. Controlled inflammation is important for fighting infection, but in excess, it becomes destructive to host cells and to the architecture of the lungs [2,3]. 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 inflamma- tory 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]. Interleukin-1 beta (IL-1b) is a major inflammatory mediator. Its physiological effects are diverse and potentially important to the pathogenesis of lung exacerbations in CF, including the generation of fever, the recruitment of inflammatory effector cells, the induction of other pro-inflammatory cytokines such as IL-6 and IL-8, and the shaping of T cell responses [9,10]. Following initiation of the NF-kB signaling cascade, IL-1b is produced in the cytosol as a biologically inactive full-length pro-IL-1b. Pro-IL-1b is subsequently converted into its active form by cytosolic protein complexes termed ‘‘inflammasomes.’’ Inflammasomes assemble in response to certain cellular danger signals and mediate the auto- activation of caspase-1 [9,11], which cleaves pro-IL-1b and pro- IL-18 into their biologically active forms for secretion. Four distinct inflammasomes have been recognized. These are the PLoS ONE | www.plosone.org 1 May 2012 | Volume 7 | Issue 5 | e37689