Immune deficiencies, infection, and systemic immune disordersAdhesion of Streptococcus pneumoniae to human airway epithelial cells exposed to urban particulate matter
Section snippets
Cells and S pneumoniae
A549, a human type II pneumocyte cell line, was obtained from Sigma-Aldrich (Poole, Dorset, United Kingdom [UK]) and maintained in Dulbecco modified Eagle medium (Invitrogen Ltd, Paisley, UK) with 10% FBS and 1% L-glutamine/penicillin-streptomycin (Lonza Ltd, Basel, Switzerland). Human primary bronchial epithelial cells (HBEpC) were obtained from the main bronchi of a healthy white male and were purchased from Promocell (Heidelberg, Germany). The virulent type 2 S pneumoniae encapsulated
Results
Culture of A549 cells with urban PM10 (UK) increased adhesion of S pneumoniae assessed by quantitative culture (P < .001 vs medium control at 50 μg/mL; Fig 1). Confocal microscopy of fluorescent S pneumoniae confirmed that PM10 (UK) stimulated a dose-dependent increase in pneumococcal adhesion to A549 cells (P < .01 vs medium control; Fig 2). Increased pneumococcal adhesion to A549 cells resulted in increased intracellular penetration of bacteria (P < .01; Fig 3). The same pattern of adhesion
Discussion
In this study, we found that inhalable PM from urban areas in both the developing world and the developed world increases the adhesion of pneumococci to human airway epithelial cells. Pneumococcal adhesion stimulated by urban PM is associated with enhanced vulnerability to cellular infection. We excluded the possibility that increased pneumococcal adhesion is due to cell death or injury by the absence of LDH release and MTT expression. Electron microscopy of PM-exposed cells showed PM attached
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Supported by Queen Mary University London.
Disclosure of potential conflict of interest: M. Ezzati receives research support from the US National Science Foundation. The rest of the authors have declared that they have no conflict of interest.