Multiple inflammasomes may regulate the interleukin-1-driven inflammation in protracted bacterial bronchitis

Alice C-H Chen; Hai B Tran; Yang Xi; Stephanie T Yerkovich; Katherine J Baines; Susan J Pizzutto; Melanie Carroll; Avril A B Robertson; Matthew A Cooper; Kate Schroder; Jodie L Simpson; Peter G Gibson; Greg Hodge; Ian B Masters; Helen M Buntain; Helen L Petsky; Samantha J Prime; Anne B Chang; Sandra Hodge; John W Upham

doi:10.1183/23120541.00130-2017

Multiple inflammasomes may regulate the interleukin-1-driven inflammation in protracted bacterial bronchitis

ERJ Open Res. 2018 Mar 23;4(1):00130-2017. doi: 10.1183/23120541.00130-2017. eCollection 2018 Jan.

Authors

Alice C-H Chen^{1

2}, Hai B Tran^{3

2}, Yang Xi¹, Stephanie T Yerkovich⁴, Katherine J Baines⁵, Susan J Pizzutto⁶, Melanie Carroll¹, Avril A B Robertson⁷, Matthew A Cooper⁷, Kate Schroder⁷, Jodie L Simpson⁵, Peter G Gibson⁵, Greg Hodge^{3

8}, Ian B Masters⁹, Helen M Buntain¹⁰, Helen L Petsky¹¹, Samantha J Prime¹², Anne B Chang^{6

12}, Sandra Hodge^{3

8

13}, John W Upham^{1

13}

Affiliations

¹ Diamantina Institute, Faculty of Medicine, The University of Queensland, Brisbane, Australia.
² Joint first authors.
³ Dept of Thoracic Medicine, Royal Adelaide Hospital, Adelaide, Australia.
⁴ The Prince Charles Hospital, Brisbane, Australia.
⁵ The University of Newcastle, Newcastle, Australia.
⁶ Child Health Division, Menzies School of Health Research, Charles Darwin Hospital, Darwin, Australia.
⁷ Institute for Molecular Bioscience, Brisbane, Australia.
⁸ Dept of Medicine, The University of Adelaide, Adelaide, Australia.
⁹ Respiratory and Sleep Medicine, Lady Cilento Children's Hospital and Children's Centre for Health Research, Queensland University of Technology, Brisbane, Australia.
¹⁰ Wesley Hospital, Brisbane, Australia.
¹¹ School of Nursing and Midwifery, Menzies Health Institute Queensland, Griffith University, Brisbane, Australia.
¹² Queensland University of Technology, Brisbane, Australia.
¹³ Joint senior authors.

Abstract

Protracted bacterial bronchitis (PBB) in young children is characterised by prolonged wet cough, prominent airway interleukin (IL)-1β expression and infection, often with nontypeable Haemophilus influenzae (NTHi). The mechanisms responsible for IL-1-driven inflammation in PBB are poorly understood. We hypothesised that the inflammation in PBB involves the NLRP3 and/or AIM2 inflammasome/IL-1β axis. Lung macrophages obtained from bronchoalveolar lavage (BAL), peripheral blood mononuclear cells (PBMCs), blood monocytes and monocyte-derived macrophages from patients with PBB and age-matched healthy controls were cultured in control medium or exposed to live NTHi. In healthy adult PBMCs, CD14⁺ monocytes contributed to 95% of total IL-1β-producing cells upon NTHi stimulation. Stimulation of PBB PBMCs with NTHi significantly increased IL-1β expression (p<0.001), but decreased NLRC4 expression (p<0.01). NTHi induced IL-1β secretion in PBMCs from both healthy controls and patients with recurrent PBB. This was inhibited by Z-YVAD-FMK (a caspase-1 selective inhibitor) and by MCC950 (a NLRP3 selective inhibitor). In PBB BAL macrophages inflammasome complexes were visualised as fluorescence specks of NLRP3 or AIM2 colocalised with cleaved caspase-1 and cleaved IL-1β. NTHi stimulation induced formation of specks of cleaved IL-1β, NLRP3 and AIM2 in PBMCs, blood monocytes and monocyte-derived macrophages. We conclude that both the NLRP3 and AIM2 inflammasomes probably drive the IL-1β-dominated inflammation in PBB.