|
|
||||||||
Guest Access | Sign In via User Name/Password |
|||||||||
* From the Meakins-Christie Laboratories (Dr. Taha) and Montreal Chest Research Institute (Drs. Laberge, Hamid, and Olivenstein), McGill University, and Ste-Justine Hospital, University of Montreal, Montreal, Quebec, Canada.
Correspondence to: Ronald Olivenstein, MD, Montreal Chest Institute, McGill University, 3650 St. Urbain St, Montreal, Quebec, Canada H2X 2P4; e-mail: rolive3{at}po-box.mcgill.ca
| Abstract |
|---|
|
|
|---|
Methods: We examined whether eotaxin, MCP-4, and IL-16 expression could be detected in induced sputum of asthmatic patients (n = 10), and whether the expression was increased compared to normal control subjects (n = 9). Eotaxin, MCP-4, and IL-16 immunoreactivity were determined by immunocytochemistry. In addition, inflammatory cells were investigated using markers for T cells (CD3), eosinophils (major basic protein [MBP]), macrophages (CD68), neutrophils (elastase), and epithelial cells (cytokeratin).
Results: Our results showed that there was a significant difference in the percentages of MBP-positive and epithelial cells between asthmatic patients and normal control subjects (p < 0.05). However, there was no difference between these two groups in the percentage of CD3-, elastase-, and CD68-positive cells. Immunoreactivity for eotaxin, MCP-4, and IL-16 was expressed in the induced sputum of all asthmatic patients, and expression of these chemotactic cytokines was significantly greater than in control subjects (p < 0.001, p < 0.005, and p < 0.001, respectively).
Conclusions: This study showed that induced sputum could be used to detect chemokines in patients with bronchial asthma, and that the upregulation of chemotactic cytokines in the airways can be seen using noninvasive techniques.
Key Words: asthma chemokines induced sputum
| Introduction |
|---|
|
|
|---|
Sputum induction by hypertonic saline solution represents a safe noninvasive tool to investigate the pathology of airway inflammation.13 14 Recently, we have shown15 elevated expression of Th2-type cytokines messenger RNA for IL-4 and IL-5 in induced sputum of asthmatic patients compared to control subjects, demonstrating the feasibility of this technique to detect cellular associated cytokine expression. Furthermore, this latter study confirmed the finding in other studies of an increased percentage of eosinophils in induced sputum of asthmatic patients compared to nonasthmatic control subjects.13
Therefore, the principal objectives of this study were to determine and compare the expression of cytokines with chemoattractant properties for eosinophils and T cells in induced sputum of asthmatic patients and in normal control subjects using immunocytochemistry. Specifically, we determined and compared the expression of MCP-4, eotaxin, and IL-16. Since airway epithelial cells are a major cellular source of MCP-4, eotaxin, and IL-16, we compared immunoreactive protein for these cytokines in both epithelial and nonepithelial cells.
| Materials and Methods |
|---|
|
|
|---|
|
Sputum Induction
Sputum induction was performed using a modification of the
method of Pin and coworkers.16
Subjects were administered
salbutamol, 200 µg, to inhibit possible bronchoconstriction during
sputum induction followed by increasing concentrations (3%, 4%, and
5%) of hypertonic saline solution generated by an ultrasonic nebulizer
(DeVilbiss Ultra-Neb 99; Sunrise Medical; Somerset, PA). The procedure
was interrupted every 2 min to measure peak expiratory flow. Subjects
were asked to rinse the mouth and blow the nose to minimize
contamination with saliva and postnasal drip and also instructed to
cough sputum into a sterile container. These procedures were repeated
sequentially for 8-min periods at each concentration unless a fall in
peak expiratory flow > 10% occurred, in which case the procedure was
terminated.
Sputum Examination
Sputum sample volumes were recorded. Sputum that was
macroscopically free of salivary contamination was selected to minimize
squamous cell contamination and processed within 2 h by a
modification of the technique described by Pizzichini and
coworkers.13
Briefly, sputum was treated by adding 2 mL of
Hanks balanced salt solution containing 0.1% dithiothreitol, with
vortexes for 2 to 3 min to homogenize the sample, 2 mL of
phosphate-buffered solution was added to stop the action of
dithiothreitol, and then the suspension was centrifuged at
300g for 10 min. The cell pellet was resuspended in
phosphate-buffered solution, and total cell counts of leukocytes and
cell viability were determined. For immunocytochemistry, coded
cytospins were briefly fixed in a solution of acetone:methanol (40:60),
air dried, and stored at - 20°C until further use.
Immunocytochemistry
Specific immunohistochemical markers for eosinophils (anti-major
basic protein [MBP]; a gift from Dr. R. Moqbel, University of
Alberta, Canada), T lymphocytes (anti-CD3; Becton-Dickinson;
Mississauga, Ontario, Canada), neutrophils (antielastase;
Becton-Dickinson), macrophages (anti-CD68; Dako Diagnostic;
Mississauga, Ontario, Canada) and epithelial cells (anticytokeratin,
CAM-5.2, is a murine monoclonal antibody) were used to detect the
phenotype of inflammatory cells recovered by sputum induction.
Immunocytochemistry was performed using a modified alkaline phosphatase
antialkaline phosphatase (APAAP) method as previously
reported.15
To detect eotaxin, MCP-4, and IL-16
immunoreactivity recovered by sputum induction, we used specific
polyclonal antibodies raised against human eotaxin and MCP-4 (supplied
by Dr. A. Luster) and a monoclonal antibody against IL-16 (clone 14.1,
a gift of Dr. D. M. Center). Briefly, slides were incubated with
the specific antibodies overnight at 4°C. After washing in
Tris-buffered saline solution, the secondary antibodies were applied
and the slides were washed in Tris-buffered saline solution and
incubated with the APAAP complex. The reaction was visualized by
alkaline-phosphatase substrate added to fast red TR (Sigma Chemical;
St. Louis, MO). All the slides were counterstained with hematoxylin and
mounted before examination. Negative control experiments were performed
in a similar manner but in the absence of the primary antibody; the
primary antibody was replaced by nonspecific mouse Ig or Tris-buffered
saline solution.
Data Analysis
Sputum samples containing < 20% of contaminating squamous
cells were considered suitable for analysis. The numbers of positive
cell markers of cellular phenotypes were counted per 1,000 total cells
excluding squamous cells with the help of a phase contrast lens. The
numbers of cells with immunoreactivity for eotaxin, MCP-4, or IL-16
were classified as epithelial (cytokeratin positive) or nonepithelial
in origin, then were counted per 500 total cells excluding squamous
cells. Positive cells were reported as the mean (range). To avoid
observer bias, slides were coded prior to analysis and read in a
blinded fashion. At least two cytospins were counted for each
immunocytochemical marker, and the mean value of these slides was
reported. Significant differences were detected by analysis of variance
and Mann-Whitney test. Correlation coefficients were determined by
using the Spearman correlation test. Significance was accepted at the
level of 95%.
| Results |
|---|
|
|
|---|
Quantification of Inflammatory Cells in Induced Sputum
The total cell count in asthmatic subjects was
4.4 x 106/L (range, 2.4 to
11.5 x 106/L), compared to
2.3 x 106/L (range, 1.1 to
4.3 x 106/L) in control subjects. Cell
viability was > 90% in all samples. The percentage of epithelial
cells in asthmatic patients was significantly increased (9.5%; range,
5.0 to 14.0%) compared to nonasthmatic subjects (0.95%; range, 0.4 to
1.5%; p < 0.05; Table 2
). Among nonepithelial cells, the percentage of MBP-positive cells in
asthmatic patients (5.06%; range, 1.8 to 9.6%) was significantly
greater than in nonasthmatic subjects (0.6%; range, 0.1 to 1.2;
p < 0.05; Table 2
). There was no significant difference between
asthmatic patients and normal control subjects in the percentage of
CD3-, CD68-, or elastase-positive cells (Table 2)
.
|
|
|
| Discussion |
|---|
|
|
|---|
The study of the mechanisms responsible for the recruitment of inflammatory cells into the airways is of primordial importance to our understanding of the pathogenesis of asthma. Recent studies3 have demonstrated the potential role of cytokines with chemoattractant activities such as C-C chemokines and IL-16 in this process. Most investigators8 11 12 have looked at the expression of these cytokines in the airways using fiberoptic techniques to retrieve bronchial biopsy specimens and BAL fluid. More recently, we and others13 14 15 have used the noninvasive technique of induced sputum to investigate the mechanisms involved in the development and persistence of airway eosinophilia in patients with asthma. IL-5, a cytokine involved in eosinophil differentiation and migration, is increased in induced sputum of asthmatic patients, and its expression correlates with parameters of lung function, demonstrating the feasibility of this technique in investigating the putative role of cytokines in airway disease.15 17 The present study was undertaken to investigate the expression in induced sputum of other cytokines with more potent and specific chemotactic activity for eosinophils. Our findings demonstrate that increased expression of eotaxin, MCP-4, and IL-16 in induced sputum may be potential markers for inflammation in asthma. Eotaxin expression in particular correlated with sputum eosinophilia. Eosinophil levels in induced sputum correlate with disease severity and with asthma exacerbations.17 It is intriguing to hypothesize that expression of cytokines such as eotaxin might correlate with asthma disease severity.
A novel finding of this study relates to the ability to detect chemoattractant cytokines in the cellular component of induced sputum. The measurement of cytokines in the fluid phase of induced sputum is less sensitive and has been associated with difficulties in reproducibility.18 19 We were able to detect cytokine immunoreactivity in all asthmatic patients. Another potential advantage of this technique relates to the possibility of determining the cellular sources of specific cytokines. Eotaxin, MCP-4, and IL-16 were present in both bronchial epithelial and nonepithelial cells, which is consistent with previous findings in lung tissues that showed that eotaxin, MCP-4, and IL-16 immunoreactivity were colocalized mainly to epithelial cells and to a lesser extent to macrophages, T cells, and eosinophils.12 20 21
Epithelial cells are believed to play a critical role in the
inflammatory response in asthma. For instance, airway epithelial cells
have been shown to synthesize RANTES (regulated upon activation,
normally T-cell expressed and secreted), MCP-4, eotaxin, IL-16, IL-8,
and others in response to proinflammatory mediators such as IL-1ß and
tumor necrosis factor-
, suggesting that these cells, in part,
contribute to the recruitment of inflammatory cells into the
airways.22
23
24
Eotaxin and MCP-4 induce eosinophil
migration in vitro.23
24
Furthermore, IL-16 has
been shown to induce CD4-bearing eosinophil migration in
vitro and in this regard was more potent than leukotriene
C4.10
IL-16 may also contribute to
the pathology of asthma through recruitment and activation of CD4+ T
cells.9
Until recently, the biological activity of epithelial cells in patients with asthma has been mainly investigated using in vitro cell cultures from epithelial cells lines and freshly isolated epithelial cells from bronchial biopsy specimens or bronchial brushings. In addition, airway epithelial cells have been recovered using bronchial wash, BAL, and induced sputum. The percentage of bronchial epithelial cells in induced sputum is comparable to bronchial wash and is much greater than in BAL, suggesting that this latter technique may be less useful to study airway epithelial cell biology.25 26 The percentage of epithelial cells in induced sputum from healthy and asthmatic subjects varies considerably in studies13 26 reported to date. The percentage of epithelial cells seen in induced sputum in this study is greater than in a previous study,13 but overlaps with findings in another study.26 This could be due to a difference in the technique used to detect the epithelial cells. Traditionally, epithelial cells are identified morphologically by microscopy or by flow cytometry, but cellular morphology might be more difficult to recognize in clinical situations where there is more epithelial cell damage27 and epithelial cells may be mistakenly misread as generic mononuclear cells. Epithelial cell numbers may be significantly underestimated using those techniques. Immunocytochemical staining with cytokeratin identifies all epithelial cells, including ciliated and nonciliated columnar epithelial cells, and thus might be a more accurate method to measure epithelial cells in sputum. In this study, epithelial cells were identified with an immunocytochemistry technique using a modified APAAP method with cytokeratin as the specific immunohistochemical marker for epithelial cells recovered by sputum induction. The current study suggests that induced sputum is particularly useful to evaluate chemokine expression in bronchial epithelial cells in asthma patients. The findings also suggest that induced sputum can be used to differentiate epithelial chemokine expression in atopic asthmatic patients compared to normal subjects.
We did not observe any difference in the percentage of sputum CD3+ T cells in asthmatic patients and normal subjects despite increases in the percentage of IL-16immunoreactive cells in asthmatic patients. The discrepancy of increased IL-16 expression and comparable CD3+ cells percentages between the two groups suggests that sputum might not reflect changes of T-cell numbers in the bronchial mucosa. There was no significant correlation of CD3+ T cells to the expression of IL-16 in induced sputum in asthmatic patients despite our previous demonstration that T cells are the major nonepithelial cellular source of IL-16 in mucosal biopsy specimens from asthmatic patients.11 The percentage of sputum CD3+ T cells was low in both asthmatic patients and normal control subjects, confirming previous findings in induced sputum in patients with asthma,13 15 25 26 and suggests that induced sputum may not be the best medium to study T-cellrelated phenomena in asthma.
In conclusion, our study confirms the predominant expression of eotaxin, MCP-4, and IL-16 in asthmatic airways. The positive correlation between eotaxin immunoreactivity and eosinophils numbers supports the potential important role of this cytokine for the development of airway eosinophilia in asthma. More importantly, our data demonstrate the utility of induced sputum as a noninvasive technique to document the presence of these chemoattractant cytokines in the airways in asthma. It is possible that the induced sputum technique might be useful to evaluate the therapeutic effects of a variety of anti-inflammatory agents on cytokine and chemokine production by airway inflammatory cells, including bronchial epithelial cells, in asthmatic patients.
| Acknowledgements |
|---|
| Footnotes |
|---|
Supported by the J. T. Costello Memorial Research Fund, the Medical Research Council of Canada, and Inspiraplex.
Received for publication August 17, 2000. Accepted for publication February 1, 2001.
| References |
|---|
|
|
|---|
/Rantes, is also a functional receptor for MCP3. J Biol Chem 270,22123-22128This article has been cited by other articles:
![]() |
J. Fan, N. M. Heller, M. Gorospe, U. Atasoy, and C. Stellato The role of post-transcriptional regulation in chemokine gene expression in inflammation and allergy Eur. Respir. J., November 1, 2005; 26(5): 933 - 947. [Abstract] [Full Text] [PDF] |
||||
![]() |
J.-W. Min, A.-S. Jang, S.-M. Park, S.-H. Lee, J.-H. Lee, S.-W. Park, and C.-S. Park Comparison of Plasma Eotaxin Family Level in Aspirin-Induced and Aspirin-Tolerant Asthma Patients Chest, November 1, 2005; 128(5): 3127 - 3132. [Abstract] [Full Text] [PDF] |
||||
![]() |
J.R. Gordon, V.A. Swystun, F. Li, X. Zhang, B.E. Davis, P. Hull, and D.W. Cockcroft Regular salbutamol use increases CXCL8 responses in asthma: relationship to the eosinophil response Eur. Respir. J., July 1, 2003; 22(1): 118 - 126. [Abstract] [Full Text] [PDF] |
||||
![]() |
H. D. Shin, L. H. Kim, B. L. Park, J. H. Jung, J. Y. Kim, I.-Y. Chung, J. S. Kim, J. H. Lee, S. H. Chung, Y. H. Kim, et al. Association of Eotaxin gene family with asthma and serum total IgE Hum. Mol. Genet., June 1, 2003; 12(11): 1279 - 1285. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. Taha, Q. Hamid, L. Cameron, and R. Olivenstein T Helper Type 2 Cytokine Receptors and Associated Transcription Factors GATA-3, c-MAF, and Signal Transducer and Activator of Transcription Factor-6 in Induced Sputum of Atopic Asthmatic Patients Chest, June 1, 2003; 123(6): 2074 - 2082. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. J. Alvarez Puebla, R. Castillo, A. Rey, N. Ortega, C. Blanco, and T. Carrillo Sputum Eosinophilia and Maximal Airway Narrowing in Dermatophagoides pteronyssinus Allergic Rhinitis Patients: Only Rhinitis or Rhinitis Plus Mild Asthma? Chest, November 1, 2002; 122(5): 1560 - 1565. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. Bandeira-Melo, K. Sugiyama, L. J. Woods, M. Phoofolo, D. M. Center, W. W. Cruikshank, and P. F. Weller IL-16 Promotes Leukotriene C4 and IL-4 Release from Human Eosinophils via CD4- and Autocrine CCR3-Chemokine-Mediated Signaling J. Immunol., May 1, 2002; 168(9): 4756 - 4763. [Abstract] [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |