An antagonist of the platelet-activating factor receptor inhibits adherence of both nontypeable Haemophilus influenzae and Streptococcus pneumoniae to cultured human bronchial epithelial cells exposed to cigarette smoke
Authors Dhar Shukla S, Fairbairn R, Gell D, Latham R, Sohal SS, Walters EH, O'Toole R
Received 17 March 2016
Accepted for publication 21 May 2016
Published 25 July 2016 Volume 2016:11(1) Pages 1647—1655
Checked for plagiarism Yes
Review by Single-blind
Peer reviewers approved by Professor Hsiao-Chi Chuang
Peer reviewer comments 3
Editor who approved publication: Dr Richard Russell
Shakti D Shukla,1,* Rory L Fairbairn,1,* David A Gell,1 Roger D Latham,1 Sukhwinder S Sohal,1,2 Eugene H Walters,1 Ronan F O’Toole1
1Breathe Well Centre, School of Medicine, Faculty of Health, University of Tasmania, Hobart, TAS, Australia; 2School of Health Sciences, Faculty of Health, University of Tasmania, Launceston, TAS, Australia
*These authors contributed equally to this work
Background: COPD is emerging as the third largest cause of human mortality worldwide after heart disease and stroke. Tobacco smoking, the primary risk factor for the development of COPD, induces increased expression of platelet-activating factor receptor (PAFr) in the lung epithelium. Nontypeable Haemophilus influenzae (NTHi) and Streptococcus pneumoniae adhere to PAFr on the luminal surface of human respiratory tract epithelial cells.
Objective: To investigate PAFr as a potential drug target for the prevention of infections caused by the main bacterial drivers of acute exacerbations in COPD patients, NTHi and S. pneumoniae.
Methods: Human bronchial epithelial BEAS-2B cells were exposed to cigarette smoke extract (CSE). PAFr expression levels were determined using immunocytochemistry and quantitative polymerase chain reaction. The epithelial cells were challenged with either NTHi or S. pneumoniae labeled with fluorescein isothiocyanate, and bacterial adhesion was measured using immunofluorescence. The effect of a well-evaluated antagonist of PAFr, WEB-2086, on binding of the bacterial pathogens to BEAS-2B cells was then assessed. In silico studies of the tertiary structure of PAFr and the binding pocket for PAF and its antagonist WEB-2086 were undertaken.
Results: PAFr expression by bronchial epithelial cells was upregulated by CSE, and significantly associated with increased bacterial adhesion. WEB-2086 reduced the epithelial adhesion by both NTHi and S. pneumoniae to levels observed for non-CSE-exposed cells. Furthermore, it was nontoxic toward the bronchial epithelial cells. In silico analyses identified a binding pocket for PAF/WEB-2086 in the predicted PAFr structure.
Conclusion: WEB-2086 represents an innovative class of candidate drugs for inhibiting PAFr-dependent lung infections caused by the main bacterial drivers of smoking-related COPD.
Keywords: airway epithelium, NTHi, pneumococci, WEB-2086, platelet-activating factor receptor, PAFr antagonist
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