+
MODEL
Respiratory Medicine (2014) xx, 1e7
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.elsevier.com/locate/rmed
Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease Reetika Suri a, Patrick Mallia b, Joanne E. Martin a, Joseph Footitt b,1, Jie Zhu b, Maria-Belen Trujillo-Torralbo b, Sebastian L. Johnston b, Jonathan Grigg a,* a Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London E1 2AT, UK b Airway Disease Infection Section, National Heart and Lung Institute, Imperial College London, London W2 1PG, UK
Received 13 November 2013; accepted 10 March 2014
KEYWORDS Platelet-activating factor receptor; Rhinovirus 16; Smoking; COPD
Summary Background: Bacteria expressing phosphorylcholine (ChoP) co-opt host-expressed plateletactivating factor receptor (PAFR) to adhere to lower airway cells. Cigarette smoke and rhinovirus (RV) infection upregulate PAFR-dependent bacterial adhesion to airway cells in vitro, and in healthy adults smoking increases the proportion of PAFR positive bronchial epithelial cells. To date the effect of chronic obstructive pulmonary disease (COPD) on smoke-induced PAFR is unknown. We therefore sought to test the hypothesis that bronchial PAFR mRNA expression is increased in smokers with chronic obstructive pulmonary disease (COPD), and further increases after RV infection. Methods: Endobronchial biopsies were obtained by fibreoptic bronchoscopy from healthy nonsmokers, smokers without airway obstruction, and smokers with COPD, before and after infection with rhinovirus (RV) serotype 16. Endobronchial PAFR mRNA expression was assessed by quantitative PCR and expressed as a ratio of glyceraldehyde-3-phosphate dehydrogenase. The distribution of PAFR was assessed by immunohistochemistry. Results: Baseline PAFR mRNA expression was increased (p < 0.05) in smokers (n Z 16), and smokers with COPD (n Z 14) compared with non-smokers (n Z 18). In RV16 infected subjects there was no increase in PAFR mRNA expression in either non-smokers (n Z 9), smokers (n Z 8), or smokers with COPD (n Z 7). PAFR immunoreactivity in all 3 groups was predominately restricted to the bronchial epithelium and submucosal glands.
* Corresponding author. Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, 4 Newark Street, London E1 2AT, UK. E-mail address: [email protected] (J. Grigg). 1
Deceased.
http://dx.doi.org/10.1016/j.rmed.2014.03.003 0954-6111/ª 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Suri R, et al., Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease, Respiratory Medicine (2014), http://dx.doi.org/10.1016/j.rmed.2014.03.003
+
MODEL
2
R. Suri et al. Conclusions: Endobronchial PAFR mRNA is increased in both smokers without airway obstruction and smokers with COPD. We found preliminary evidence that RV16 infection does not increase PAFR mRNA expression in either smokers or smokers with COPD. ª 2014 Elsevier Ltd. All rights reserved.
Background
Methods
Exacerbations of chronic obstructive pulmonary disease (COPD) result from an interaction between external factors such as smoking and viral infection, and host innate immune responses [1]. Wilkinson et al. [2] for example, reported that 20% of COPD exacerbations are associated with a rhinovirus (RV) infection, and patients with both RV and bacterial infection (predominately Haemophilus influenzae and/or Streptococcus pneumoniae) have increased airway inflammation and poorer clinical outcomes [2,25]. Smoking not only causes COPD, but also increases vulnerability to airway bacterial infection and invasive pneumococcal disease in its own right [3,4]. A putative mechanism for increased vulnerability of the lower airway to bacterial infection is an increased capacity of airway cells to support bacterial adhesion. In vitro studies suggest that for phosphorycholine (ChoP)-expressing bacteria such as S. pneumoniae [5,6], and H. influenzae [6,7], adhesion is enhanced by increased expression of platelet-activating factor receptor (PAFR) on host cells. During the resulting interaction, bacterial ChoP is a molecular mimic of PAF. Thus ChoP-expressing bacteria have the capacity to both adhere to PAFR, and to move across the cell membrane as the receptor is internalised. Wide range stimuli have been reported to increase PAFR-dependent adhesion of ChoP-expressing bacteria to airway epithelial cells. These include acid [8], interleukin 1a [5], RV infection [9], and cigarette smoke [10,14]. But to date, data on PAFR expression in the human lung are limited. In a recent pilot study, we found an increased proportion of PAFR-positive epithelial cells in bronchial biopsies from smokers with normal lung function compared with non-smokers [10]. By contrast, in the only other study using human lung tissue, Shirasaki et al. [11] reported decreased PAFR mRNA expression in peripheral lung biopsy specimens in 4 smokers compared with 8 controls and no PAFR mRNA expression on airway epithelial cells e the major site for clinically relevant bacterial adhesion. However in human turbinates, PAFR immunoreactivity has been reported in both the submucosal glands and epithelial cells [12]. To date, the effect of smoking on airway PAFR expression in COPD is unknown. We hypothesised that i) PAFR is increased in bronchial biopsies of current smokers with COPD compared with healthy controls, and ii) PAFR expression is increased by RV infection. In the present study, we sought to test this hypothesis using stored endobronchial biopsies from a study of healthy subjects, smokers with normal lung function, and smokers with COPD [13].
Subjects Endobronchial biopsies were obtained from an experimental RV infection study that recruited human volunteers in London (UK). Data on bacterial infection, symptoms and antimicrobial peptides have been previously reported [13]. Three groups were studied; i) healthy non-smokers (controls), ii) smokers without airway obstruction, and iii) smokers with moderate COPD (Gold stage II). Bronchoscopy, endobronchial biopsy, bronchoalveolar lavage, and induced sputum were carried out at baseline before RV serotype 16 (RV16) inoculation as previously described [13]. Endobronchial biopsy was repeated on day 7 after RV inoculation. Informed consent was obtained from all subjects (Research Ethics Committee approval 07/ H0712/138, and 11/LO/0400).
Rhinovirus inoculation and detection Ten tissue culture infective doses 50% of RV16 were diluted in a total volume of 1 ml of 0.9% saline and inoculated in both nostrils using an atomizer (No. 286; DeVilbiss Co., Heston, UK). Rhinovirus infection was defined as; either a positive RV culture or qPCR, in nasal lavage/sputum/bronchoalveolar lavage, or RV seroconversion defined as a titre of serum neutralising antibodies to RV of at least 1:4 at 6 wk. Serology was performed at screening and 6 wk postinfection by microneutralisation test for neutralising antibody to rhinovirus. Infection with viruses other than RV was excluded by testing nasal lavage samples at baseline and at the peak of upper respiratory symptoms with PCR.
Endobronchial biopsy Subjects were premedicated with nebulised salbutamol (2.5 mg) and intravenous midazolam (2e10 mg). Lignocaine gel and solutions (1e4%) were used for topical anesthesia. Bronchoscopy was performed using an Olympus BF 1T20 (Olympus Optical Co., Tokyo, Japan), and biopsies were taken from the lower lobe subcarinae and were snap frozen in liquid nitrogen and stored at 70 C for analysis of PAFR mRNA.
PAFR mRNA Endobronchial biopsy tissue was homogenised and the RNA extracted using the RNAeasy kit (Qiagen, Crawley, UK). First strand cDNA was synthesised using SuperScript VILO master mix according to manufacturer’s instructions (Life
Please cite this article in press as: Suri R, et al., Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease, Respiratory Medicine (2014), http://dx.doi.org/10.1016/j.rmed.2014.03.003
+
MODEL
Bronchial PAFR in COPD Table 1
3
Subject Demographics and endobronchial PAFR mRNA expression.
n Age (yr) Body mass index (kg m2) Females (n) Smoking pack years (n) FEV1 (% predicted) FVC (% predicted) FEV1/FVC Baseline (day 0) PAFR mRNA expression PAFR mRNA expression at day 7 in rhinovirus-infected subjects
Non-smokers
Smokers
Smokers with COPD
18 59.2 1.6 25.2 1.0 9 0 112.3 4.4 124.4 4.8 73.9 1.2 1.17 0.01 n Z 18 1.19 0.01 (n Z 9)
16 54.3 1.8 27.1 0.9 7 33.25 2.21 102.9 3.4 117.5 3.0 71.6 1.1 1.22 0.01a n Z 16 1.16 0.03 (n Z 8)
14 59.6 2.2 25.7 1.1 5 39.35 2.24 64 3.4 95.0 3.5 54.3 2.7 1.23 0.01a n Z 14 1.25 0.03 (n Z 7)
Data are summarised as mean (standard error of mean). FEV1; forced expiratory volume in 1 s, FVC; forced vital capacity. PAFR; platelet-activating factor receptor mRNA expression was determined by qPCR and expressed relative to the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH). a p < 0.05 vs. non smokers by unpaired t test. There is no difference in PAFR between the 3 groups at day 7.
technologies, Paisley, UK). mRNA transcript level of PAFR and the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were determined by quantitative real-time PCR using an ABI 7500 real-time PCR system (Applied Biosystems, Warrington, UK) with TaqMan primer and probe sets Hs00265399_S1 (PAFR) and Hs02758991_g1 (GAPDH). RT-PCR reactions were carried out in triplicate. The PAFR to housekeeping gene ratio was generated for each sample.
Immunohistochemistry Antigen retrieval was carried out in on 3 mm paraffin wax embedded sections dried down overnight at 60 C. Sections were dewaxed through graded alcohols and then placed in an EDTA buffer of pH8.1 and microwaved at full power for 35 min. The slides were then transferred to a DAKO Autostainer where they were treated with a 3% peroxidase block followed by the Vector R.T.U Vectastain Kit (PK-7200), according to manufacturer’s recommendations. The working dilution of the human anti-PAFR monoclonal antibody CAY160600 (Cayman Chemical, Cambridge Bioscience, UK) was 1:100 and the incubation time was 40 min. The signal was visualised using DAKO DAB þ Chromogen solution (K3468) applied for 5 min. A Gills haematoxylin nuclei counterstain was used for 2 min and differentiated accordingly. A negative control using tonsil tissue without the anti-PAFR antibody showed no non-specific DAB signal.
Statistical analysis Data are summarised as mean (SEM). Differences were analysed by t test and Dunnett’s multiple comparisons test. Correlations were expressed by Pearson correlation coefficient (r). Analyses were performed using GraphPad Prism version 6.00b for Mac (GraphPad Software, San Diego, CA). Differences were considered significant at p < 0.05.
Results Stored endobronchial tissue for PAFR mRNA at baseline (i.e. pre-RV infection) was available from 18 non-smokers, 16 smokers, and 14 smokers with COPD (Table 1). Baseline paraffin-embedded samples for PAFR immunostaining was limited to 7 controls, 7 smokers, and 7 smokers with COPD. There was no significant difference in age or body mass index between the 3 groups (Table 1). In subjects who developed a RV16 infection, paired baseline and day 7 (post-infection) biopsies were available from 9 nonsmokers, 8 smokers, and 7 smokers with COPD.
Figure 1 Baseline platelet-activating factor receptor (PAFR) mRNA expression in endobronchial tissue in non-smokers, smokers without airway obstruction, and smokers with COPD. PAFR mRNA expression was measured by quantitative PCR and expressed relative to the house-keeping gene glyceraldehyde3-phosphate dehydrogenase (GAPDH). PAFR is increased in both smokers and smokers with COPD * p < 0.05 vs. nonsmokers, by unpaired t test and Dunnett’s multiple comparisons test. There is no difference in PAFR mRNA between smokers and smokers with COPD (p Z NS, Dunnett’s multiple comparisons test). Bar represents mean.
Please cite this article in press as: Suri R, et al., Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease, Respiratory Medicine (2014), http://dx.doi.org/10.1016/j.rmed.2014.03.003
+
MODEL
4 Baseline endobronchial PAFR mRNA expression relative to the GADPH housekeeping gene was increased in both smokers and smokers with COPD (p < 0.05 vs. non smokers, Fig. 1, Table 1). There was no difference in PAFR mRNA expression between smokers and smokers with COPD (p Z NS, Dunnett’s multiple comparisons test), and no significant correlation between baseline PAFR mRNA expression and pack years in either smokers, or smokers with COPD. PAFR-positive pseudostratified airway epithelial cells were present in all 21 paraffin-embedded baseline sections (Fig. 2(A)). Furthermore, PAFR-positive goblet cells were prominent in both smokers and smokers with COPD (Fig. 2(B)). PAFR-positive cells in bronchial submucosal glands were also found in all 10 subjects where bronchial submucosal glands were included in the section (controls n Z 4, smokers n Z 3, and smoking with COPD n Z 3). PAFR positivity of other cells, such as smooth muscle cells, was
R. Suri et al. either minimal or absent (Fig. 2(A) and (B)). PAFR immunostaining in smokers and smokers with COPD was not uniform since expression was lower in areas of squamous metaplasia (Fig. 2(D)). Squamous metaplasia was not found in healthy controls. The small number of samples available, and the patchy nature of staining precluded quantitation of PAFR immunoreactivity by image analysis. Rhinovirus infection did not increase PAFR mRNA expression in either non-smokers, smokers, or smokers with COPD (Fig. 3, p Z NS, paired t test). Cross-sectional analysis in RV-infected subjects at day 7 showed no difference in PAFR mRNA between the groups (Fig. 4, Table 1).
Discussion In this study we sought to assess the hypothesis that endobronchial PAFR mRNA expression is increased in
Figure 2 A. Platelet-activating factor receptor (PAFR) staining (brown) in endobronchial biopsy tissue from a non-smoking subject. PAFR expression is predominately limited to normal airway epithelium (arrow). Bar represents 100 microns. B Plateletactivating factor receptor (PAFR) expression (brown) in an endobronchial biopsy from a smoking subject with COPD. There are PAFR positive goblet cells at the bronchial air-tissue interface (arrow). Bar represents 100 microns. C. Platelet-activating factor receptor (PAFR) expression of bronchial mucosal glands (arrow) in an endobronchial biopsy from a smoker with COPD. Bar represents 100 microns. D. Comparison of platelet-activating factor receptor expression in an area of squamous metaplasia (SM) with an area of more normal epithelium (N) in a smoking subject. Bar represents 100 microns. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Please cite this article in press as: Suri R, et al., Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease, Respiratory Medicine (2014), http://dx.doi.org/10.1016/j.rmed.2014.03.003
+
MODEL
Bronchial PAFR in COPD
Figure 3 Paired change in endobronchial platelet-activating factor receptor (PAFR) mRNA expression between baseline and day 7 post-inoculation in subjects who developed a rhinovirus infection; (A) non-smokers, (B) smokers, (C) smokers with COPD. PAFR mRNA is expressed relative to GAPDH. PAFR mRNA expression did not change in any group (p Z NS, paired t test).
smokers with COPD. Compatible with this hypothesis and our previous data from healthy smokers [10], we found increased PAFR mRNA expression in both smokers and smokers with COPD. There was no difference in PAFR mRNA between smokers with COPD and smokers without airway obstruction, suggesting that smoking, and not COPD is the major stimulus for PAFR expression in vivo. Indeed epidemiological studies suggest that, exposure to cigarette smoke is a major risk factor for invasive pneumococcal disease in immunocompetent adults [4]. We focused on
5 PAFR, since animal and in vitro models suggest that increased epithelial PAFR expression increases vulnerability to bacterial infection in both the lung [5,15,16] and the gut [17]. But to date the evidence that PAFR is expressed on airway cells in vivo is contradictory. On one hand, Shirasaki et al. [11] using in situ hybridisation reported no evidence of PAFR mRNA expression in airway epithelial cells in human lung tissue. On the other hand, we previously found an increased proportion of PAFR-positive airway epithelial cells in smokers without airway obstruction [10]. Immunostaining of the limited number of biopsy samples in the present study found that PAFR is expressed by airway epithelial cells e confirming our previous findings and extending this to both goblet cells and bronchial submucosal glands. The variability of PAFR immunostaining in smokers and smokers with COPD, and the small amounts of stored tissue meant that quantification of cell-specific expression would be biased and was therefore not done. However qualitative analysis showed that most PAFR-positive cells were either located at the bronchial surface (epithelial cells and goblet cells) or lining submucosal glands that open into the airway. It is therefore likely that these cells are major contributors to increased PAFR mRNA expression in smokers and smokers with COPD. Indeed, in vitro studies report a close association between upregulation of PAFR mRNA expression in epithelial cells and both surface PAFR expression and PAFRdependent bacterial adhesion [8,18]. Our data suggest that future studies of PAFR-dependent adhesion should focus on goblet and bronchial submucosal cells. Indeed in a guinea pig model of COPD, an increase in the number of airway goblet cells induced by chronic exposure to cigarette smoke is significantly attenuated by treatment with a specific antagonist of PAFR [20]. Whether increased endobronchial PAFR mRNA expression in smokers and smokers with COPD increases their capacity to support pneumococcal adhesion is unclear. Indirect evidence of the functional relevance of PAFR is provided by the observation of increased adherence of pneumococci to buccal and pharyngeal epithelial cells in smokers [21,22]. In COPD however, pneumococcal adherence to bronchial epithelial and oropharyngeal cells is not increased [23]. RV infection increases PAFR expression and PAFRdependent adhesion of S. pneumoniae to nasal epithelial cells [24] and human tracheal epithelial cells in vitro [9]. The present study is the first study to evaluate the effect of RV infection on PAFR expression in vivo. Following RV16 infection we found no increase in PAFR mRNA in COPD subjects, smokers or non-smoking controls. There was however, a trend towards increased PAFR in the RVinfected non-smoking controls, (p Z 0.09). Although these data do not support our hypothesis that RV infection increases PAFR mRNA, the limited number of subjects studied means an effect of RV infection cannot be excluded e especially in controls. Future studies should therefore include larger subject numbers, and additional time points. Both experimental [13] and naturally-acquired RV infections in patients with COPD are associated with not only S. pneumoniae but also other bacteria such as H. influenzae [26]. Although H. influenzae can utilise PAFR it also binds to host cells via a number of other receptors including carcinoembryonic antigen cell adhesion molecules 1 and 3,
Please cite this article in press as: Suri R, et al., Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease, Respiratory Medicine (2014), http://dx.doi.org/10.1016/j.rmed.2014.03.003
+
MODEL
6
R. Suri et al. PF (deceased); performed the experimental infection study, JZ; processed and sectioned the bronchial biopsies, MT; recruited subjects into the experimental infection study, and contributed to sample collection, SJ; conceived the experimental rhinovirus infection study, supervised the clinical study and contributed to the final draft, JG; conceived the PAFR study, wrote the first draft of the manuscript, and is responsible for overall data integrity.
Conflict of interest statement
Figure 4 Platelet-activating factor receptor (PAFR) mRNA expression at day 7 in endobronchial tissue in subjects who developed a rhinovirus infection. PAFR was measured by quantitative PCR and expressed relative to the house-keeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH). There is no significant differences between groups (p Z NS, Dunnett’s multiple comparisons test). Bar represents mean.
fibronectin, laminin, intercellular adhesion molecule-1 and respiratory epithelial mucins [19]. The effects of RV infection on these cellular receptors therefore warrant further study to investigate their role in post-RV secondary infections due to H. influenzae. The discrepancies between the in vitro and in vivo effects of RV on PAFR highlight the importance of carrying out such studies in vivo in COPD subjects. In conclusion, the study found that endobronchial PAFR mRNA expression is increased in both smokers and smokers with COPD compared with healthy controls, and that RV16 infection does not further increase PAFR mRNA. Immunohistochemical analysis showed PAFR-positive cells predominately located at the bronchial air-tissue interface. These data suggest that blocking of PAFR by, for example, second generation antihistamines [27], may reduce bacterial adhesion to airway cells of smokers and smokers with COPD.
Funding The human RV infection studies were funded by Medical Research Council Programme Grant G0600879, Wellcome Trust Grant 083567/Z/07/Z for the Centre for Respiratory Infection, Imperial College and the National Institute for Health Research (NIHR) Biomedical Research Centre funding scheme, the NIHR Clinical Lecturer funding scheme (PM & JF), an unrestricted grant from GlaxoSmithKline and a grant from Pfizer UK. The PAFR study was funded by Queen Mary University London.
Statement of authorship RS; did the PAFR analysis, statistical analysis, and contributed to the final draft, PM; performed the experimental infection study, and contributed to the final draft, JM assessed immunostaining and contributed to the final draft,
Reetika Suri; no conflict of interest. Patrick Mallia; no conflict of interest. Joanne E Martin; no conflict of interest. Joseph Footitt (deceased). Jie Zhu; no conflict of interest. Maria-Belen Trujillo-Torralbo; no conflict of interest. Sebastian L. Johnston; no conflict of interest. Jonathan Grigg; I have received honoraria from Novartis and GlaxoSMithKline for advisory board membership (paediatric asthma).
References [1] Decramer M, Janssens W, Miravitlles M. Chronic obstructive pulmonary disease. Lancet 2012;379:1341e51. [2] Wilkinson TM, Hurst JR, Perera WR, et al. Effect of interactions between lower airway bacterial and rhinoviral infection in exacerbations of copd. Chest 2006;129:317e24. [3] Garmendia J, Morey P, Bengoechea JA. Impact of cigarette smoke exposure on host-bacterial pathogen interactions. Eur Respir J 2012;39:467e77. [4] Nuorti JP, Butler JC, Farley MM, et al. Cigarette smoking and invasive pneumococcal disease. Active bacterial core surveillance team. N Engl J Med 2000;342:681e9. [5] Cundell DR, Gerard NP, Gerard C, et al. Streptococcus pneumoniae anchor to activated human cells by the receptor for platelet-activating factor. Nature 1995;377:435e8. [6] Yokota S, Okabayashi T, Yoto Y, et al. Fosfomycin suppresses rs-virus-induced streptococcus pneumoniae and haemophilus influenzae adhesion to respiratory epithelial cells via the platelet-activating factor receptor. FEMS Microbiol Lett 2010; 310:84e90. [7] Swords WE, Buscher BA, Ver Steeg Ii K, et al. Non-typeable haemophilus influenzae adhere to and invade human bronchial epithelial cells via an interaction of lipooligosaccharide with the paf receptor. Mol Microbiol 2000;37:13e27. [8] Ishizuka S, Yamaya M, Suzuki T, et al. Acid exposure stimulates the adherence of streptococcus pneumoniae to cultured human airway epithelial cells: effects on platelet-activating factor receptor expression. Am J Respir Cell Mol Biol 2001; 24:459e68. [9] Ishizuka S, Yamaya M, Suzuki T, et al. Effects of rhinovirus infection on the adherence of streptococcus pneumoniae to cultured human airway epithelial cells. J Infect Dis 2003;188: 1928e39. [10] Grigg J, Walters H, Sohal SS, et al. Cigarette smoke and platelet-activating factor receptor dependent adhesion of streptococcus pneumoniae to lower airway cells. Thorax 2012; 67:908e13. [11] Shirasaki H, Nishikawa M, Adcock IM, et al. Expression of platelet-activating factor receptor mrna in human and guinea pig lung. Am J Respir Cell Mol Biol 1994;10:533e7.
Please cite this article in press as: Suri R, et al., Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease, Respiratory Medicine (2014), http://dx.doi.org/10.1016/j.rmed.2014.03.003
+
MODEL
Bronchial PAFR in COPD [12] Shirasaki H, Seki N, Kikuchi M, et al. Expression and localization of platelet-activating factor receptor in human nasal mucosa. Ann Allergy Asthma Immunol 2005;95:190e6. [13] Mallia P, Footitt J, Sotero R, et al. Rhinovirus infection induces degradation of antimicrobial peptides and secondary bacterial infection in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2012;186:1117e24. [14] Greenberg D, Givon-Lavi N, Broides A, et al. The contribution of smoking and exposure to tobacco smoke to streptococcus pneumoniae and haemophilus influenzae carriage in children and their mothers. Clin Infect Dis 2006;42:897e903. [15] Duitman J, Schouten M, Groot AP, et al. Ccaat/enhancerbinding protein delta facilitates bacterial dissemination during pneumococcal pneumonia in a platelet-activating factor receptor-dependent manner. Proc Natl Acad Sci U S A 2012; 109:9113e8. [16] Rijneveld AW, Weijer S, Florquin S, et al. Improved host defense against pneumococcal pneumonia in plateletactivating factor receptor-deficient mice. J Infect Dis 2004; 189:711e6. [17] Keely S, Glover LE, Weissmueller T, et al. Hypoxia-inducible factor-dependent regulation of platelet-activating factor receptor as a route for gram-positive bacterial translocation across epithelia. Mol Biol Cell 2010;21:538e46. [18] Mutepe ND, Cockeran R, Steel HC, et al. Effects of cigarette smoke condensate on pneumococcal biofilm formation and pneumolysin. Eur Respir J 2013;41:392e5. [19] Avadhanula V, Rodriguez CA, Ulett GC, et al. Nontypeable haemophilus influenzae adheres to intercellular adhesion
7
[20]
[21]
[22]
[23]
[24]
[25]
[26]
[27]
molecule 1 (icam-1) on respiratory epithelial cells and upregulates icam-1 expression. Infect Immun 2006;74:830e8. Komori M, Inoue H, Matsumoto K, et al. Paf mediates cigarette smoke-induced goblet cell metaplasia in guinea pig airways. Am J Physiol Lung Cell Mol Physiol 2001;280:L436e41. Raman AS, Swinburne AJ, Fedullo AJ. Pneumococcal adherence to the buccal epithelial cells of cigarette smokers. Chest 1983;83:23e7. Fainstein V, Musher DM. Bacterial adherence to pharyngeal cells in smokers, nonsmokers, and chronic bronchitics. Infect Immun 1979;26:178e82. Riise GC, Larsson S, Andersson BA. Bacterial adhesion to oropharyngeal and bronchial epithelial cells in smokers with chronic bronchitis and in healthy nonsmokers. Eur Respir J 1994;7:1759e64. Wang JH, Kwon HJ, Jang YJ. Rhinovirus enhances various bacterial adhesions to nasal epithelial cells simultaneously. Laryngoscope 2009;119:1406e11. Launes C, de-Sevilla MF, Selva L, et al. Viral coinfection in children less than five years old with invasive pneumococcal disease. Pediatr Infect Dis J 2012;31:650e3. Hutchinson AF, Ghimire AK, Thompson MA, et al. A communitybased, time-matched, case-control study of respiratory viruses and exacerbations of copd. Respir Med 2007;101:2472e81. Izquierdo I, Merlos M, Garcia-Rafanell J. Rupatadine: a new selective histamine h1 receptor and platelet-activating factor (paf) antagonist. A review of pharmacological profile and clinical management of allergic rhinitis. Drugs Today (Barc) 2003;39:451e68.
Please cite this article in press as: Suri R, et al., Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease, Respiratory Medicine (2014), http://dx.doi.org/10.1016/j.rmed.2014.03.003
MODEL
Respiratory Medicine (2014) xx, 1e7
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.elsevier.com/locate/rmed
Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease Reetika Suri a, Patrick Mallia b, Joanne E. Martin a, Joseph Footitt b,1, Jie Zhu b, Maria-Belen Trujillo-Torralbo b, Sebastian L. Johnston b, Jonathan Grigg a,* a Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London E1 2AT, UK b Airway Disease Infection Section, National Heart and Lung Institute, Imperial College London, London W2 1PG, UK
Received 13 November 2013; accepted 10 March 2014
KEYWORDS Platelet-activating factor receptor; Rhinovirus 16; Smoking; COPD
Summary Background: Bacteria expressing phosphorylcholine (ChoP) co-opt host-expressed plateletactivating factor receptor (PAFR) to adhere to lower airway cells. Cigarette smoke and rhinovirus (RV) infection upregulate PAFR-dependent bacterial adhesion to airway cells in vitro, and in healthy adults smoking increases the proportion of PAFR positive bronchial epithelial cells. To date the effect of chronic obstructive pulmonary disease (COPD) on smoke-induced PAFR is unknown. We therefore sought to test the hypothesis that bronchial PAFR mRNA expression is increased in smokers with chronic obstructive pulmonary disease (COPD), and further increases after RV infection. Methods: Endobronchial biopsies were obtained by fibreoptic bronchoscopy from healthy nonsmokers, smokers without airway obstruction, and smokers with COPD, before and after infection with rhinovirus (RV) serotype 16. Endobronchial PAFR mRNA expression was assessed by quantitative PCR and expressed as a ratio of glyceraldehyde-3-phosphate dehydrogenase. The distribution of PAFR was assessed by immunohistochemistry. Results: Baseline PAFR mRNA expression was increased (p < 0.05) in smokers (n Z 16), and smokers with COPD (n Z 14) compared with non-smokers (n Z 18). In RV16 infected subjects there was no increase in PAFR mRNA expression in either non-smokers (n Z 9), smokers (n Z 8), or smokers with COPD (n Z 7). PAFR immunoreactivity in all 3 groups was predominately restricted to the bronchial epithelium and submucosal glands.
* Corresponding author. Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, 4 Newark Street, London E1 2AT, UK. E-mail address: [email protected] (J. Grigg). 1
Deceased.
http://dx.doi.org/10.1016/j.rmed.2014.03.003 0954-6111/ª 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Suri R, et al., Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease, Respiratory Medicine (2014), http://dx.doi.org/10.1016/j.rmed.2014.03.003
+
MODEL
2
R. Suri et al. Conclusions: Endobronchial PAFR mRNA is increased in both smokers without airway obstruction and smokers with COPD. We found preliminary evidence that RV16 infection does not increase PAFR mRNA expression in either smokers or smokers with COPD. ª 2014 Elsevier Ltd. All rights reserved.
Background
Methods
Exacerbations of chronic obstructive pulmonary disease (COPD) result from an interaction between external factors such as smoking and viral infection, and host innate immune responses [1]. Wilkinson et al. [2] for example, reported that 20% of COPD exacerbations are associated with a rhinovirus (RV) infection, and patients with both RV and bacterial infection (predominately Haemophilus influenzae and/or Streptococcus pneumoniae) have increased airway inflammation and poorer clinical outcomes [2,25]. Smoking not only causes COPD, but also increases vulnerability to airway bacterial infection and invasive pneumococcal disease in its own right [3,4]. A putative mechanism for increased vulnerability of the lower airway to bacterial infection is an increased capacity of airway cells to support bacterial adhesion. In vitro studies suggest that for phosphorycholine (ChoP)-expressing bacteria such as S. pneumoniae [5,6], and H. influenzae [6,7], adhesion is enhanced by increased expression of platelet-activating factor receptor (PAFR) on host cells. During the resulting interaction, bacterial ChoP is a molecular mimic of PAF. Thus ChoP-expressing bacteria have the capacity to both adhere to PAFR, and to move across the cell membrane as the receptor is internalised. Wide range stimuli have been reported to increase PAFR-dependent adhesion of ChoP-expressing bacteria to airway epithelial cells. These include acid [8], interleukin 1a [5], RV infection [9], and cigarette smoke [10,14]. But to date, data on PAFR expression in the human lung are limited. In a recent pilot study, we found an increased proportion of PAFR-positive epithelial cells in bronchial biopsies from smokers with normal lung function compared with non-smokers [10]. By contrast, in the only other study using human lung tissue, Shirasaki et al. [11] reported decreased PAFR mRNA expression in peripheral lung biopsy specimens in 4 smokers compared with 8 controls and no PAFR mRNA expression on airway epithelial cells e the major site for clinically relevant bacterial adhesion. However in human turbinates, PAFR immunoreactivity has been reported in both the submucosal glands and epithelial cells [12]. To date, the effect of smoking on airway PAFR expression in COPD is unknown. We hypothesised that i) PAFR is increased in bronchial biopsies of current smokers with COPD compared with healthy controls, and ii) PAFR expression is increased by RV infection. In the present study, we sought to test this hypothesis using stored endobronchial biopsies from a study of healthy subjects, smokers with normal lung function, and smokers with COPD [13].
Subjects Endobronchial biopsies were obtained from an experimental RV infection study that recruited human volunteers in London (UK). Data on bacterial infection, symptoms and antimicrobial peptides have been previously reported [13]. Three groups were studied; i) healthy non-smokers (controls), ii) smokers without airway obstruction, and iii) smokers with moderate COPD (Gold stage II). Bronchoscopy, endobronchial biopsy, bronchoalveolar lavage, and induced sputum were carried out at baseline before RV serotype 16 (RV16) inoculation as previously described [13]. Endobronchial biopsy was repeated on day 7 after RV inoculation. Informed consent was obtained from all subjects (Research Ethics Committee approval 07/ H0712/138, and 11/LO/0400).
Rhinovirus inoculation and detection Ten tissue culture infective doses 50% of RV16 were diluted in a total volume of 1 ml of 0.9% saline and inoculated in both nostrils using an atomizer (No. 286; DeVilbiss Co., Heston, UK). Rhinovirus infection was defined as; either a positive RV culture or qPCR, in nasal lavage/sputum/bronchoalveolar lavage, or RV seroconversion defined as a titre of serum neutralising antibodies to RV of at least 1:4 at 6 wk. Serology was performed at screening and 6 wk postinfection by microneutralisation test for neutralising antibody to rhinovirus. Infection with viruses other than RV was excluded by testing nasal lavage samples at baseline and at the peak of upper respiratory symptoms with PCR.
Endobronchial biopsy Subjects were premedicated with nebulised salbutamol (2.5 mg) and intravenous midazolam (2e10 mg). Lignocaine gel and solutions (1e4%) were used for topical anesthesia. Bronchoscopy was performed using an Olympus BF 1T20 (Olympus Optical Co., Tokyo, Japan), and biopsies were taken from the lower lobe subcarinae and were snap frozen in liquid nitrogen and stored at 70 C for analysis of PAFR mRNA.
PAFR mRNA Endobronchial biopsy tissue was homogenised and the RNA extracted using the RNAeasy kit (Qiagen, Crawley, UK). First strand cDNA was synthesised using SuperScript VILO master mix according to manufacturer’s instructions (Life
Please cite this article in press as: Suri R, et al., Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease, Respiratory Medicine (2014), http://dx.doi.org/10.1016/j.rmed.2014.03.003
+
MODEL
Bronchial PAFR in COPD Table 1
3
Subject Demographics and endobronchial PAFR mRNA expression.
n Age (yr) Body mass index (kg m2) Females (n) Smoking pack years (n) FEV1 (% predicted) FVC (% predicted) FEV1/FVC Baseline (day 0) PAFR mRNA expression PAFR mRNA expression at day 7 in rhinovirus-infected subjects
Non-smokers
Smokers
Smokers with COPD
18 59.2 1.6 25.2 1.0 9 0 112.3 4.4 124.4 4.8 73.9 1.2 1.17 0.01 n Z 18 1.19 0.01 (n Z 9)
16 54.3 1.8 27.1 0.9 7 33.25 2.21 102.9 3.4 117.5 3.0 71.6 1.1 1.22 0.01a n Z 16 1.16 0.03 (n Z 8)
14 59.6 2.2 25.7 1.1 5 39.35 2.24 64 3.4 95.0 3.5 54.3 2.7 1.23 0.01a n Z 14 1.25 0.03 (n Z 7)
Data are summarised as mean (standard error of mean). FEV1; forced expiratory volume in 1 s, FVC; forced vital capacity. PAFR; platelet-activating factor receptor mRNA expression was determined by qPCR and expressed relative to the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH). a p < 0.05 vs. non smokers by unpaired t test. There is no difference in PAFR between the 3 groups at day 7.
technologies, Paisley, UK). mRNA transcript level of PAFR and the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were determined by quantitative real-time PCR using an ABI 7500 real-time PCR system (Applied Biosystems, Warrington, UK) with TaqMan primer and probe sets Hs00265399_S1 (PAFR) and Hs02758991_g1 (GAPDH). RT-PCR reactions were carried out in triplicate. The PAFR to housekeeping gene ratio was generated for each sample.
Immunohistochemistry Antigen retrieval was carried out in on 3 mm paraffin wax embedded sections dried down overnight at 60 C. Sections were dewaxed through graded alcohols and then placed in an EDTA buffer of pH8.1 and microwaved at full power for 35 min. The slides were then transferred to a DAKO Autostainer where they were treated with a 3% peroxidase block followed by the Vector R.T.U Vectastain Kit (PK-7200), according to manufacturer’s recommendations. The working dilution of the human anti-PAFR monoclonal antibody CAY160600 (Cayman Chemical, Cambridge Bioscience, UK) was 1:100 and the incubation time was 40 min. The signal was visualised using DAKO DAB þ Chromogen solution (K3468) applied for 5 min. A Gills haematoxylin nuclei counterstain was used for 2 min and differentiated accordingly. A negative control using tonsil tissue without the anti-PAFR antibody showed no non-specific DAB signal.
Statistical analysis Data are summarised as mean (SEM). Differences were analysed by t test and Dunnett’s multiple comparisons test. Correlations were expressed by Pearson correlation coefficient (r). Analyses were performed using GraphPad Prism version 6.00b for Mac (GraphPad Software, San Diego, CA). Differences were considered significant at p < 0.05.
Results Stored endobronchial tissue for PAFR mRNA at baseline (i.e. pre-RV infection) was available from 18 non-smokers, 16 smokers, and 14 smokers with COPD (Table 1). Baseline paraffin-embedded samples for PAFR immunostaining was limited to 7 controls, 7 smokers, and 7 smokers with COPD. There was no significant difference in age or body mass index between the 3 groups (Table 1). In subjects who developed a RV16 infection, paired baseline and day 7 (post-infection) biopsies were available from 9 nonsmokers, 8 smokers, and 7 smokers with COPD.
Figure 1 Baseline platelet-activating factor receptor (PAFR) mRNA expression in endobronchial tissue in non-smokers, smokers without airway obstruction, and smokers with COPD. PAFR mRNA expression was measured by quantitative PCR and expressed relative to the house-keeping gene glyceraldehyde3-phosphate dehydrogenase (GAPDH). PAFR is increased in both smokers and smokers with COPD * p < 0.05 vs. nonsmokers, by unpaired t test and Dunnett’s multiple comparisons test. There is no difference in PAFR mRNA between smokers and smokers with COPD (p Z NS, Dunnett’s multiple comparisons test). Bar represents mean.
Please cite this article in press as: Suri R, et al., Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease, Respiratory Medicine (2014), http://dx.doi.org/10.1016/j.rmed.2014.03.003
+
MODEL
4 Baseline endobronchial PAFR mRNA expression relative to the GADPH housekeeping gene was increased in both smokers and smokers with COPD (p < 0.05 vs. non smokers, Fig. 1, Table 1). There was no difference in PAFR mRNA expression between smokers and smokers with COPD (p Z NS, Dunnett’s multiple comparisons test), and no significant correlation between baseline PAFR mRNA expression and pack years in either smokers, or smokers with COPD. PAFR-positive pseudostratified airway epithelial cells were present in all 21 paraffin-embedded baseline sections (Fig. 2(A)). Furthermore, PAFR-positive goblet cells were prominent in both smokers and smokers with COPD (Fig. 2(B)). PAFR-positive cells in bronchial submucosal glands were also found in all 10 subjects where bronchial submucosal glands were included in the section (controls n Z 4, smokers n Z 3, and smoking with COPD n Z 3). PAFR positivity of other cells, such as smooth muscle cells, was
R. Suri et al. either minimal or absent (Fig. 2(A) and (B)). PAFR immunostaining in smokers and smokers with COPD was not uniform since expression was lower in areas of squamous metaplasia (Fig. 2(D)). Squamous metaplasia was not found in healthy controls. The small number of samples available, and the patchy nature of staining precluded quantitation of PAFR immunoreactivity by image analysis. Rhinovirus infection did not increase PAFR mRNA expression in either non-smokers, smokers, or smokers with COPD (Fig. 3, p Z NS, paired t test). Cross-sectional analysis in RV-infected subjects at day 7 showed no difference in PAFR mRNA between the groups (Fig. 4, Table 1).
Discussion In this study we sought to assess the hypothesis that endobronchial PAFR mRNA expression is increased in
Figure 2 A. Platelet-activating factor receptor (PAFR) staining (brown) in endobronchial biopsy tissue from a non-smoking subject. PAFR expression is predominately limited to normal airway epithelium (arrow). Bar represents 100 microns. B Plateletactivating factor receptor (PAFR) expression (brown) in an endobronchial biopsy from a smoking subject with COPD. There are PAFR positive goblet cells at the bronchial air-tissue interface (arrow). Bar represents 100 microns. C. Platelet-activating factor receptor (PAFR) expression of bronchial mucosal glands (arrow) in an endobronchial biopsy from a smoker with COPD. Bar represents 100 microns. D. Comparison of platelet-activating factor receptor expression in an area of squamous metaplasia (SM) with an area of more normal epithelium (N) in a smoking subject. Bar represents 100 microns. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Please cite this article in press as: Suri R, et al., Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease, Respiratory Medicine (2014), http://dx.doi.org/10.1016/j.rmed.2014.03.003
+
MODEL
Bronchial PAFR in COPD
Figure 3 Paired change in endobronchial platelet-activating factor receptor (PAFR) mRNA expression between baseline and day 7 post-inoculation in subjects who developed a rhinovirus infection; (A) non-smokers, (B) smokers, (C) smokers with COPD. PAFR mRNA is expressed relative to GAPDH. PAFR mRNA expression did not change in any group (p Z NS, paired t test).
smokers with COPD. Compatible with this hypothesis and our previous data from healthy smokers [10], we found increased PAFR mRNA expression in both smokers and smokers with COPD. There was no difference in PAFR mRNA between smokers with COPD and smokers without airway obstruction, suggesting that smoking, and not COPD is the major stimulus for PAFR expression in vivo. Indeed epidemiological studies suggest that, exposure to cigarette smoke is a major risk factor for invasive pneumococcal disease in immunocompetent adults [4]. We focused on
5 PAFR, since animal and in vitro models suggest that increased epithelial PAFR expression increases vulnerability to bacterial infection in both the lung [5,15,16] and the gut [17]. But to date the evidence that PAFR is expressed on airway cells in vivo is contradictory. On one hand, Shirasaki et al. [11] using in situ hybridisation reported no evidence of PAFR mRNA expression in airway epithelial cells in human lung tissue. On the other hand, we previously found an increased proportion of PAFR-positive airway epithelial cells in smokers without airway obstruction [10]. Immunostaining of the limited number of biopsy samples in the present study found that PAFR is expressed by airway epithelial cells e confirming our previous findings and extending this to both goblet cells and bronchial submucosal glands. The variability of PAFR immunostaining in smokers and smokers with COPD, and the small amounts of stored tissue meant that quantification of cell-specific expression would be biased and was therefore not done. However qualitative analysis showed that most PAFR-positive cells were either located at the bronchial surface (epithelial cells and goblet cells) or lining submucosal glands that open into the airway. It is therefore likely that these cells are major contributors to increased PAFR mRNA expression in smokers and smokers with COPD. Indeed, in vitro studies report a close association between upregulation of PAFR mRNA expression in epithelial cells and both surface PAFR expression and PAFRdependent bacterial adhesion [8,18]. Our data suggest that future studies of PAFR-dependent adhesion should focus on goblet and bronchial submucosal cells. Indeed in a guinea pig model of COPD, an increase in the number of airway goblet cells induced by chronic exposure to cigarette smoke is significantly attenuated by treatment with a specific antagonist of PAFR [20]. Whether increased endobronchial PAFR mRNA expression in smokers and smokers with COPD increases their capacity to support pneumococcal adhesion is unclear. Indirect evidence of the functional relevance of PAFR is provided by the observation of increased adherence of pneumococci to buccal and pharyngeal epithelial cells in smokers [21,22]. In COPD however, pneumococcal adherence to bronchial epithelial and oropharyngeal cells is not increased [23]. RV infection increases PAFR expression and PAFRdependent adhesion of S. pneumoniae to nasal epithelial cells [24] and human tracheal epithelial cells in vitro [9]. The present study is the first study to evaluate the effect of RV infection on PAFR expression in vivo. Following RV16 infection we found no increase in PAFR mRNA in COPD subjects, smokers or non-smoking controls. There was however, a trend towards increased PAFR in the RVinfected non-smoking controls, (p Z 0.09). Although these data do not support our hypothesis that RV infection increases PAFR mRNA, the limited number of subjects studied means an effect of RV infection cannot be excluded e especially in controls. Future studies should therefore include larger subject numbers, and additional time points. Both experimental [13] and naturally-acquired RV infections in patients with COPD are associated with not only S. pneumoniae but also other bacteria such as H. influenzae [26]. Although H. influenzae can utilise PAFR it also binds to host cells via a number of other receptors including carcinoembryonic antigen cell adhesion molecules 1 and 3,
Please cite this article in press as: Suri R, et al., Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease, Respiratory Medicine (2014), http://dx.doi.org/10.1016/j.rmed.2014.03.003
+
MODEL
6
R. Suri et al. PF (deceased); performed the experimental infection study, JZ; processed and sectioned the bronchial biopsies, MT; recruited subjects into the experimental infection study, and contributed to sample collection, SJ; conceived the experimental rhinovirus infection study, supervised the clinical study and contributed to the final draft, JG; conceived the PAFR study, wrote the first draft of the manuscript, and is responsible for overall data integrity.
Conflict of interest statement
Figure 4 Platelet-activating factor receptor (PAFR) mRNA expression at day 7 in endobronchial tissue in subjects who developed a rhinovirus infection. PAFR was measured by quantitative PCR and expressed relative to the house-keeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH). There is no significant differences between groups (p Z NS, Dunnett’s multiple comparisons test). Bar represents mean.
fibronectin, laminin, intercellular adhesion molecule-1 and respiratory epithelial mucins [19]. The effects of RV infection on these cellular receptors therefore warrant further study to investigate their role in post-RV secondary infections due to H. influenzae. The discrepancies between the in vitro and in vivo effects of RV on PAFR highlight the importance of carrying out such studies in vivo in COPD subjects. In conclusion, the study found that endobronchial PAFR mRNA expression is increased in both smokers and smokers with COPD compared with healthy controls, and that RV16 infection does not further increase PAFR mRNA. Immunohistochemical analysis showed PAFR-positive cells predominately located at the bronchial air-tissue interface. These data suggest that blocking of PAFR by, for example, second generation antihistamines [27], may reduce bacterial adhesion to airway cells of smokers and smokers with COPD.
Funding The human RV infection studies were funded by Medical Research Council Programme Grant G0600879, Wellcome Trust Grant 083567/Z/07/Z for the Centre for Respiratory Infection, Imperial College and the National Institute for Health Research (NIHR) Biomedical Research Centre funding scheme, the NIHR Clinical Lecturer funding scheme (PM & JF), an unrestricted grant from GlaxoSmithKline and a grant from Pfizer UK. The PAFR study was funded by Queen Mary University London.
Statement of authorship RS; did the PAFR analysis, statistical analysis, and contributed to the final draft, PM; performed the experimental infection study, and contributed to the final draft, JM assessed immunostaining and contributed to the final draft,
Reetika Suri; no conflict of interest. Patrick Mallia; no conflict of interest. Joanne E Martin; no conflict of interest. Joseph Footitt (deceased). Jie Zhu; no conflict of interest. Maria-Belen Trujillo-Torralbo; no conflict of interest. Sebastian L. Johnston; no conflict of interest. Jonathan Grigg; I have received honoraria from Novartis and GlaxoSMithKline for advisory board membership (paediatric asthma).
References [1] Decramer M, Janssens W, Miravitlles M. Chronic obstructive pulmonary disease. Lancet 2012;379:1341e51. [2] Wilkinson TM, Hurst JR, Perera WR, et al. Effect of interactions between lower airway bacterial and rhinoviral infection in exacerbations of copd. Chest 2006;129:317e24. [3] Garmendia J, Morey P, Bengoechea JA. Impact of cigarette smoke exposure on host-bacterial pathogen interactions. Eur Respir J 2012;39:467e77. [4] Nuorti JP, Butler JC, Farley MM, et al. Cigarette smoking and invasive pneumococcal disease. Active bacterial core surveillance team. N Engl J Med 2000;342:681e9. [5] Cundell DR, Gerard NP, Gerard C, et al. Streptococcus pneumoniae anchor to activated human cells by the receptor for platelet-activating factor. Nature 1995;377:435e8. [6] Yokota S, Okabayashi T, Yoto Y, et al. Fosfomycin suppresses rs-virus-induced streptococcus pneumoniae and haemophilus influenzae adhesion to respiratory epithelial cells via the platelet-activating factor receptor. FEMS Microbiol Lett 2010; 310:84e90. [7] Swords WE, Buscher BA, Ver Steeg Ii K, et al. Non-typeable haemophilus influenzae adhere to and invade human bronchial epithelial cells via an interaction of lipooligosaccharide with the paf receptor. Mol Microbiol 2000;37:13e27. [8] Ishizuka S, Yamaya M, Suzuki T, et al. Acid exposure stimulates the adherence of streptococcus pneumoniae to cultured human airway epithelial cells: effects on platelet-activating factor receptor expression. Am J Respir Cell Mol Biol 2001; 24:459e68. [9] Ishizuka S, Yamaya M, Suzuki T, et al. Effects of rhinovirus infection on the adherence of streptococcus pneumoniae to cultured human airway epithelial cells. J Infect Dis 2003;188: 1928e39. [10] Grigg J, Walters H, Sohal SS, et al. Cigarette smoke and platelet-activating factor receptor dependent adhesion of streptococcus pneumoniae to lower airway cells. Thorax 2012; 67:908e13. [11] Shirasaki H, Nishikawa M, Adcock IM, et al. Expression of platelet-activating factor receptor mrna in human and guinea pig lung. Am J Respir Cell Mol Biol 1994;10:533e7.
Please cite this article in press as: Suri R, et al., Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease, Respiratory Medicine (2014), http://dx.doi.org/10.1016/j.rmed.2014.03.003
+
MODEL
Bronchial PAFR in COPD [12] Shirasaki H, Seki N, Kikuchi M, et al. Expression and localization of platelet-activating factor receptor in human nasal mucosa. Ann Allergy Asthma Immunol 2005;95:190e6. [13] Mallia P, Footitt J, Sotero R, et al. Rhinovirus infection induces degradation of antimicrobial peptides and secondary bacterial infection in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2012;186:1117e24. [14] Greenberg D, Givon-Lavi N, Broides A, et al. The contribution of smoking and exposure to tobacco smoke to streptococcus pneumoniae and haemophilus influenzae carriage in children and their mothers. Clin Infect Dis 2006;42:897e903. [15] Duitman J, Schouten M, Groot AP, et al. Ccaat/enhancerbinding protein delta facilitates bacterial dissemination during pneumococcal pneumonia in a platelet-activating factor receptor-dependent manner. Proc Natl Acad Sci U S A 2012; 109:9113e8. [16] Rijneveld AW, Weijer S, Florquin S, et al. Improved host defense against pneumococcal pneumonia in plateletactivating factor receptor-deficient mice. J Infect Dis 2004; 189:711e6. [17] Keely S, Glover LE, Weissmueller T, et al. Hypoxia-inducible factor-dependent regulation of platelet-activating factor receptor as a route for gram-positive bacterial translocation across epithelia. Mol Biol Cell 2010;21:538e46. [18] Mutepe ND, Cockeran R, Steel HC, et al. Effects of cigarette smoke condensate on pneumococcal biofilm formation and pneumolysin. Eur Respir J 2013;41:392e5. [19] Avadhanula V, Rodriguez CA, Ulett GC, et al. Nontypeable haemophilus influenzae adheres to intercellular adhesion
7
[20]
[21]
[22]
[23]
[24]
[25]
[26]
[27]
molecule 1 (icam-1) on respiratory epithelial cells and upregulates icam-1 expression. Infect Immun 2006;74:830e8. Komori M, Inoue H, Matsumoto K, et al. Paf mediates cigarette smoke-induced goblet cell metaplasia in guinea pig airways. Am J Physiol Lung Cell Mol Physiol 2001;280:L436e41. Raman AS, Swinburne AJ, Fedullo AJ. Pneumococcal adherence to the buccal epithelial cells of cigarette smokers. Chest 1983;83:23e7. Fainstein V, Musher DM. Bacterial adherence to pharyngeal cells in smokers, nonsmokers, and chronic bronchitics. Infect Immun 1979;26:178e82. Riise GC, Larsson S, Andersson BA. Bacterial adhesion to oropharyngeal and bronchial epithelial cells in smokers with chronic bronchitis and in healthy nonsmokers. Eur Respir J 1994;7:1759e64. Wang JH, Kwon HJ, Jang YJ. Rhinovirus enhances various bacterial adhesions to nasal epithelial cells simultaneously. Laryngoscope 2009;119:1406e11. Launes C, de-Sevilla MF, Selva L, et al. Viral coinfection in children less than five years old with invasive pneumococcal disease. Pediatr Infect Dis J 2012;31:650e3. Hutchinson AF, Ghimire AK, Thompson MA, et al. A communitybased, time-matched, case-control study of respiratory viruses and exacerbations of copd. Respir Med 2007;101:2472e81. Izquierdo I, Merlos M, Garcia-Rafanell J. Rupatadine: a new selective histamine h1 receptor and platelet-activating factor (paf) antagonist. A review of pharmacological profile and clinical management of allergic rhinitis. Drugs Today (Barc) 2003;39:451e68.
Please cite this article in press as: Suri R, et al., Bronchial platelet-activating factor receptor in chronic obstructive pulmonary disease, Respiratory Medicine (2014), http://dx.doi.org/10.1016/j.rmed.2014.03.003
