Cigarette smoke and platelet-activating factor receptor dependent adhesion of Streptococcus pneumoniae to lower airway cells

Grigg, Jonathan
Walters, Haydn
Sohal, Sukhwinder Singh
Wood-Baker, Richard
Reid, David W
Xu, Cang-Bao
Edvinsson, Lars
Morissette, Mathieu C
Stämpfli, Martin R
Kirwan, Michael
Koh, Lee
Suri, Reetika
Mushtaq, Naseem

¹Centre for Paediatrics, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
²NHMRC National Centre for Research Excellence in Chronic Respiratory Disease, Menzies Research Institute, Hobart, Australia
³Division of Experimental Vascular Research, Institute of Clinical Science in Lund, Lund University, Lund, Sweden
⁴Departments of Pathology and Molecular Medicine, McMaster Immunology Research Centre, McMaster University, Hamilton, Ontario, Canada

Professor Jonathan Grigg, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary, University of London, 4 Newark Street, London E1 2AT, UK; [email protected]

Received July 21, 2011

Accepted April 5, 2012

Thorax 67(10):p 908-913, October 2012. | DOI: 10.1136/thoraxjnl-2011-200835

Background

Exposure to cigarette smoke (CS) is associated with increased risk of pneumococcal infection. The mechanism for this association is unknown. We recently reported that the particulate matter from urban air simulates platelet-activating factor receptor (PAFR)-dependent adhesion of pneumococci to airway cells. We therefore sought to determine whether CS stimulates pneumococcal adhesion to airway cells.

Methods

Human alveolar (A549), bronchial (BEAS2-B), and primary bronchial epithelial cells (HBEpC) were exposed to CS extract (CSE), and adhesion of Streptococcus pneumoniae determined. The role of PAFR in mediating adhesion was determined using a blocker (CV-3988). PAFR transcript level was assessed by quantitative real-time PCR, and PAFR expression by flow cytometry. Lung PAFR transcript level was assessed in mice exposed to CS, and bronchial epithelial PAFR expression assessed in active-smokers by immunostaining.

Results

In A549 cells, CSE 1% increased pneumococcal adhesion (p<0.05 vs control), PAFR transcript level (p<0.01), and PAFR expression (p<0.01). Pneumococcal adhesion to A549 cells was attenuated by CV-3988 (p<0.001). CSE 1% stimulated pneumococcal adhesion to BEAS2-B cells and HBEpC (p<0.01 vs control). CSE 1% increased PAFR expression in BEAS2-B (p<0.01), and in HBEpC (p<0.05). Lung PAFR transcript level was increased in mice exposed to CS in vivo (p<0.05 vs room air). Active smokers (n=16) had an increased percentage of bronchial epithelium with PAFR-positive cells (p<0.05 vs never smokers, n=11).

Conclusion

CSE stimulates PAFR-dependent pneumococcal adhesion to lower airway epithelial cells. We found evidence that CS increases bronchial PAFR in vivo.