HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:
Guest Access | Sign In via User Name/Password

This Article Abstract Full Text (PDF) Free Online supplemental file Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Add to My Personal Article Archive Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Innes, A. L. Articles by Fahy, J. V. Search for Related Content PubMed PubMed Citation Articles by Innes, A. L. Articles by Fahy, J. V.

Epithelial Mucin Stores Are Increased in the Large Airways of Smokers With Airflow Obstruction^*

^* From the Department of Medicine, Division of Pulmonary and Critical Care Medicine, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA.

Correspondence to: John V. Fahy, MD, Box 0111, University of California, San Francisco, 505 Parnassus Ave, San Francisco, CA 94143; e-mail: john.fahy{at}ucsf.edu.

Abstract

Background: Habitual cigarette smoking is associated with chronic mucus hypersecretion, but the relationship between mucus abnormalities and airflow obstruction in smokers is uncertain.

Methods: We collected bronchial biopsy samples and epithelial brushings from 24 smokers with and without airflow obstruction and 19 nonsmoking healthy control subjects. Epithelial mucin stores, mucin immunostains, and goblet cell morphology were quantified in bronchial biopsy samples using stereology, and mucin gene expression was quantified in epithelial brushings using real-time reverse transcriptase-polymerase chain reaction.

Results: Goblet cell size and number were higher than normal in smokers (both p < 0.05), leading to a 2.2-fold increase in the volume of stored mucin in the epithelium per surface area of basal lamina (1.94 ± 0.31 µm³/µm² vs 4.32 ± 0.55 µm³/µm² in control subjects vs smokers, p = 0.001). The increase in stored mucin occurred because of an increase in MUC5AC (p = 0.018) and despite a decrease in MUC5B (p < 0.0001). Stored mucin was significantly higher in the subgroup of smokers with airflow obstruction (p = 0.029) and correlated with FEV₁/FVC even when controlling for diffusing capacity as a measure of emphysema (p = 0.034).

Conclusions: Epithelial mucin stores are increased in habitual smokers because of goblet cell hypertrophy and hyperplasia, and the pattern of mucin gene expression is abnormal. The highest epithelial mucin stores are found in smokers with airflow obstruction, suggesting a mechanistic link between epithelial mucin dysregulation and airflow obstruction.

Key Words: airway epithelium • cigarette smoke • COPD • mucin • MUC2 • MUC6 • MUC5AC • MUC5B • stereology

The mechanisms of airway remodeling leading to airflow obstruction in habitual smokers are not well understood. One possibility is that smoking damages the airway epithelium, thereby promoting airway infection. Normally, the airway is defended from exogenous insults by the secreted mucus layer, which traps invading pathogens and propels them out of the lung by the mucociliary escalator.¹ Airflow obstruction in smokers may therefore be the consequence of recurrent airway infections, occurring because of smoking-induced increases in airway mucus and poor mucus clearance (a concept known as the British hypothesis).²³

Pathology studies⁴⁵⁶ demonstrate that the airways of habitual smokers are characterized by goblet cell metaplasia and proliferation of submucosal glands. The consequence of these changes is the subject of debate. Although goblet cell metaplasia and gland proliferation provide an explanation for the sputum symptoms that occur in habitual smokers, the relationships between sputum symptoms, airway infections, and airflow obstruction have been difficult to determine in clinical studies. The initial studies of Fletcher et al⁷ suggested no relationship between severity of sputum symptoms, frequency of airway infections, and development of airflow obstruction. But subsequent studies⁸⁹ have suggested otherwise, and there is now a growing consensus that exacerbations of chronic bronchitis play a role in accelerated loss of lung function in smokers, and that sputum symptoms are more than an epiphenomenon.¹⁰¹¹

Resistance to airflow in smokers occurs largely because of increased resistance in small airways¹²; this knowledge has led to doubt about the relevance of large airway pathology, such as changes in goblet cells and glands as well as the sputum symptoms that reflect this pathology. But central airway pathology may indirectly reflect peripheral airway pathology because both occur as a consequence of susceptibility to cigarette smoke. Also, poor mucus clearance in the central airways could have consequences for the health and sterility of small airways because mucus retention centrally will adversely affect mucus clearance from more peripheral airways and may even result in peripheral aspiration of mucus originating in large airways.

In this study, we set out to explore structure-function relationships in the airways of habitual smokers with an emphasis on goblet cell mucins in the large airways. Although a study¹³ has reported no relationship between mucin markers in central airways and airflow in smokers, we applied developed quantitative methods (based on design-based stereology) to measure mucin content and composition in central airways, and to relate those measures to degree of airflow obstruction. Stereology has advantages in morphology studies because it provides unbiased quantitative estimates of tissue structure and protein expression that are well suited to structure-function correlations.^14151617

Materials and Methods

Subjects
We enrolled 24 cigarette smokers (defined as current smoking of at least 10 cigarettes per day and a minimum history of 10 pack-years of exposure) and 19 nonsmoking control subjects (defined as < 10 pack-years of smoking with no smoking in the previous 10 years). For all subjects, inclusion criterion was age 30 to 65 years. Exclusion criteria were as follows: FEV₁/FVC < 0.4; provocative concentration of methacholine resulting in 20% decrease in FEV₁ from baseline value (PC₂₀) [< 1 mg/mL]; history of asthma; recent upper respiratory tract infection; significant medical problems other than smoking-related lung disease; history of home oxygen use; or admission to an ICU for respiratory failure. The study was approved by the University of California, San Francisco Committee on Human Research, and all subjects provided signed informed consent.

Subjects completed two visits 1 week apart. At visit 1, subjects provided medical history and underwent physical examination, spirometry, and methacholine challenge; the subjects also underwent 12-lead ECG and determination of single-breath diffusing capacity for carbon monoxide (DLCO) [details in on-line supplement[. Measurements for DLCO were made after a minimum 4-h hold of cigarette smoking for all smokers. Subjects also completed a detailed respiratory questionnaire, which included the following questions: "Do you cough on most days for 3 consecutive months or more during a 12-month period?" and "Do you bring up phlegm on most days for 3 consecutive months or more during a 12-month period?." After each question, subjects were asked to indicate the number of years that they have had those symptoms.

At visit 2, FEV₁/FVC was measured before and 20 min after albuterol, 360 µg, in all subjects; smokers with a postbronchodilator FEV₁/FVC < 0.7 were categorized as having airway obstruction.¹⁸ Bronchoscopy was performed, and bronchial biopsy specimens and epithelial brushings were collected. Biopsy specimens were processed in formalin and paraffin. Tissue sections were cut and stained with Alcian-blue periodic acid-Schiff and with immunostaining protocols specific for MUC2, MUC5AC, and MUC5B. Stereology was used to quantify goblet cells and mucin outcomes.¹⁶ Primary outcome measurements were made on 5.0 ± 1.5 biopsies and 99 ± 58 fields per subject (mean± SD). Bronchial brushings were processed to allow quantification of messenger RNA transcripts for mucin genes, using methods of real-time reverse transcriptase-polymerase chain reaction¹⁹ (details for methods in on-line supplement).

Statistics
Baseline characteristics, morphometric outcomes, and messenger RNA copy numbers for genes of interest (log transformed for normality) were compared in smokers and nonsmokers using Student t test and rank-sum test. Three-group comparisons were performed using analysis of variance, with p values for subsequent pairwise comparisons adjusted using the Sidak correction.²⁰ We developed multivariate linear regression models to examine the relationship between airflow obstruction (postbronchodilator FEV₁/FVC) and morphometric outcomes while controlling for potential confounders and diffusing capacity as a measure of emphysema. Data analysis was performed using STATA 5.0 (StataCorp; College Station, TX). All tests were two sided; p < 0.05 indicated statistical significance.

Results

The baseline clinical characteristics of the 24 smokers and the 19 nonsmoking control subjects showed that more of the smokers were male, and that the smokers were older and had lower values for FEV₁ and FEV₁/FVC (Table 1 ). Although on average the smokers were more hyperresponsive to methacholine than the healthy subjects (Table 1), 17 of the 24 smokers had PC₂₀ in the normal range (> 8 mg/mL). Sixteen of the 24 smokers had DLCO in the normal range (> 80% of predicted). All 19 healthy subjects were lifetime nonsmokers with one exception, a subject with a distant 4-pack-year smoking history. Of the 24 smokers, 9 had airflow obstruction (postbronchodilator FEV₁/FVC < 0.7). Compared to the 15 smokers without airflow obstruction, the 9 with obstruction had a higher pack-year smoking history, lower DLCO, and lower PC₂₀ (Table 2 ). By the Global Initiative for Chronic Obstructive Lung Disease classification¹⁸ of COPD severity, three subjects were stage 0, four were stage I, and five were stage II.

View larger version (133K): [in this window] [in a new window] [Download PPT slide]   Figure 1. Photomicrographs of representative sections from endobronchial biopsies from healthy subjects (left panels) and smokers (right panels). Mucin stores in goblet cells appear as a mixture of blue and purple when stained sequentially with Alcian-blue and periodic acid-Schiff stains (top left, A and top right, B). Note that mucin staining in the epithelium is more prominent than normal in smokers because of goblet cell hypertrophy and hyperplasia. Different gel-forming mucins detected with specific antibodies appear as brown immunostains (center left, C through bottom right, F). MUC5AC immunostain is higher than normal in smokers (center left, C and center right, D), whereas MUC5B immunostains are lower than normal (bottom left, E and bottom right, F). Sizebar = 20 µm; original x 2,000.

View larger version (17K): [in this window] [in a new window] [Download PPT slide]   Figure 2. The volume of stored mucin per surface area of basal lamina in the bronchial epithelium of healthy subjects and smokers (left) and in the subgroups of smokers with (n = 9) and without (n = 15) airflow obstruction (right). Data are presented as mean ± SE.

To determine whether the relative proportions of various gel-forming mucins in the airway epithelium are changed in smokers, we performed immunohistochemical studies using antibodies for the principal gel-forming mucins: MUC5AC, MUC5B, MUC2, and MUC6. We found that MUC5AC immunostaining in the surface airway epithelium (Fig 1, center left, C and center right, D) was 80% higher in smokers than nonsmoking control subjects (p < 0.05; Table 3). In contrast, surface MUC5B immunostaining (Fig 1, bottom left, E and bottom right, F) was fivefold lower in smokers (n = 24) than nonsmoking control subjects (n = 15) [p < 0.0001, Table 3]. MUC2 immunostaining was detectable in goblet cells but at much lower levels than either MUC5AC or MUC5B, with similar staining in smokers (n = 24) and nonsmoking control subjects (n = 15) [Table 3]. MUC6 was undetectable in the goblet cells and submucosal gland cells of one nonsmoking control subject and two smokers in formalin-fixed and paraffin-embedded tissue blocks (on-line supplement Fig 1). In addition, MUC6 was undetectable in goblet cells in frozen bronchial biopsy sections of from three smokers. A positive control (sections of human gastric mucosa, formalin fixed, and paraffin embedded) exhibited intense MUC6 staining in mucus-secreting cells of the crypts (on-line supplement Fig 1).

In additional analyses, we developed multivariate linear regression models to examine the relationship between FEV₁/FVC (outcome variable) and goblet cell size, goblet cell number, and stores of specific mucin proteins (assessed by immunohistochemistry) in our smokers while controlling for potential confounders (age, sex, pack-years of smoking, PC₂₀, and DLCO; on-line supplement Table 3). These analyses suggest additional morphologic abnormalities in the mucus-producing apparatus of the airway epithelium that correlate with degree of airflow obstruction in smokers, including mean goblet cell volume, number of goblet cells in the epithelium, and volume of staining for MUC5AC and MUC2.

To confirm our immunohistochemical studies for the gel-forming mucins, we quantified the gene expression of the gel-forming mucins using two-step real-time reverse transcriptase-polymerase chain reaction.¹⁹ We found an abnormal pattern of gene expression in smokers that mirrored the immunohistochemical findings (Table 5 ). Specifically, we found that expression of MUC5AC in smokers was higher than in healthy control subjects, and expression of MUC5B in smokers was lower than in healthy control subjects (Table 5).

Discussion

We report that goblet cell hypertrophy and hyperplasia occur in the large airways of habitual cigarette smokers and result in epithelial mucin stores that are significantly higher than normal. The increase in stored mucin occurs because of an increase in MUC5AC and despite a decrease in MUC5B. Notably, the highest epithelial mucin stores are in the smoker subgroup with airflow obstruction, and mucin stores correlate with FEV₁/FVC, even when controlling for diffusing capacity as a measure of emphysema. These findings suggest that smoking-induced increases in epithelial mucins may contribute to mechanisms of smoking-induced airflow obstruction.

Goblet cell hyperplasia has been described in the small airways of smokers with COPD,⁵²¹ and increased MUC5AC has been described in large airways of smokers,¹³ but our data are novel in several ways. First, using methods of stereology, which permit precise estimates of mucin volume and the size and number of goblet cells, we show that the twofold increase in epithelial mucin stores in smokers occurs because of the combined effects of goblet cell hypertrophy and hyperplasia. Second, we show that MUC5AC is not the only gel-forming mucin whose expression is altered in smokers, but that MUC5B expression is also significantly decreased. Third, we show that the increases in epithelial mucins are higher in smokers with airflow obstruction than without.

Stereology provides quantitative estimates of outcomes such as number, volume, and surface area by providing methods for converting two-dimensional information from tissue sections into three-dimensional estimates.¹⁴¹⁵ The term design-based stereology acknowledges that strategies for avoiding measurement bias begin with the experimental design and includes methods of tissue embedding, such as the isector method used here and described previously.¹⁵ In these ways, stereology accounts for the volume bias inherent in two-dimensional sections and also enables accurate estimates of orientation-sensitive outcomes, such as surface area and thickness.

Our finding that MUC5AC protein is increased in the airway epithelium in smokers is in agreement with a report¹³ in similar subject populations. However, those authors report no significant change in MUC5B expression in smokers, whereas we report a large and statistically significant decrease. The difference in our results may reflect differences in methods, including choice of MUC5B antibody and the methods used to quantify the immunostains. The decrease in MUC5B protein that we found using our methods is corroborated by a similarly large and significant reduction in MUC5B gene expression in epithelial brushings. These changes in the relative amounts of MUC5AC and MUC5B in smokers are difficult to interpret because not much is known about the specific properties of the protein products of different gel-forming mucins. However, it is reasonable to hypothesize that changes from normal in stored mucins will be reflected in similar changes in secreted mucins. These changes could have deleterious consequences for the mucus gel matrix if they disturb the optimal physiology of the gel and render epithelial cells more vulnerable to airborne toxins. The alternative hypothesis—that these mucin changes are a protective response that is helpful to the host—also needs to be considered. In this regard, the mucociliary apparatus has adaptive capacities that can benefit the host in response to noxious environmental stimuli. However, there is likely a point at which abnormal concentrations of mucins in secretions render cilia less efficient, the gel less transportable, and the airway less healthy. Genetic perturbations in the mucociliary apparatus, such as those that occur in immotile cilia syndrome and cystic fibrosis, demonstrate that the consequences of a poorly functioning mucociliary apparatus are airway infection and airflow obstruction, two characteristics of smoking-associated airway disease.

We found that epithelial mucin stores are higher in smokers with airflow obstruction than smokers without. Not all previously published studies have found this relationship. Researchers in two pathology studies have, like us, examined lung tissue from well-characterized smokers. O’Donnell et al¹³ measured epithelial mucins in smokers but found no difference between smokers with and without airflow obstruction. In contrast, Hogg et al²² found that progression of airflow obstruction in smokers is associated with mucous plugs in the lumen of small airways. Epithelial mucin stores were not quantified, but several other remodeling changes in the small airways of smokers were described,²² specifically thickening of the airway wall. These findings and our own lead us to consider that increased epithelial mucins in smokers may occur in the context of other remodeling changes—such as collagen deposition—that can affect airflow. The time course for the development of epithelial and mesenchymal remodeling in smokers may differ, however. For example, one possibility is that smoking-induced changes in epithelial mucins occur early, promote epithelial cell activation, and thereby initiate mesenchymal remodeling directed by epithelial cell mediators.²³

Goblet cells are not the only source of mucins in the airway. Mucous cells in submucosal glands also contribute mucins to airway secretions, and enlargement of submucosal glands has been found in autopsy studies of patients with COPD.⁴²⁴ However, it is unknown if changes in submucosal glands occur in smokers with only mild airway disease such as those described here, or if the goblet cell changes we observed may occur independently of changes in submucosal glands. These questions were not addressed by our study.

Whether the smoking-associated changes in epithelial mucin stores and epithelial mucin gene expression that we have observed are reversible is uncertain. The Lung Health Study²⁵ found that symptoms of cough and sputum production in smokers with chronic bronchitis improve during the first year after smoking cessation. Similarly, cytologic examination of tracheobronchial cells in the sputum of smokers entering a smoking cessation program suggested a decrease in sputum mucus and mucous cell metaplasia in sustained quitters over the course of 1 year.²⁶ On the basis of those results, one might speculate that goblet cell hypertrophy and hyperplasia improve over a similar time course with smoking cessation; however, we are not aware of any studies that have studied this directly.

In summary, we find that the airway epithelium of habitual cigarette smokers is characterized by hypertrophy and hyperplasia of goblet cells leading to increased stores of gel-forming mucins. In addition, the pattern of expression of gel-forming mucins is abnormal in smokers, with an increase in MUC5AC and a decrease in MUC5B. Finally, the levels of stored mucins in the epithelium are highest in smokers with airflow obstruction, suggesting a mechanistic link between epithelial mucin dysregulation and airflow obstruction. Such a link raises the possibility that therapies that normalize epithelial mucins may improve airflow obstruction in smokers.

Acknowledgements

The authors thank the following staff at University of California, San Francisco for assistance with this study: Peggy Cadbury and Hofer Wong for recruiting subjects and for assistance with bronchoscopy; and Roderick Carter and Ronald Ferrando for assistance in tissue processing and analysis. The authors also thank Mimi Zeiger for editing the manuscript and Ingemar Carlstedt for the generous contribution of the monoclonal antibodies LUM2-3 and LUM5B-2.

Footnotes

Abbreviations: DLCO = single-breath diffusing capacity for carbon monoxide; PC₂₀ = provocative concentration of methacholine resulting in 20% decrease in FEV₁ from baseline value

Drs. Innes and Woodruff contributed equally to the article.

This work was performed at the University of California, San Francisco.

The authors have no financial or potential conflicts of interest.

Financial support was provided by an RO1 grant (HL66564) to Dr. Fahy from the National Heart, Lung, and Blood Institute, and by a K23 award (RR17002) to Dr. Woodruff from the National Center for Research Resources. In addition, Dr. Innes was supported by an institutional training grant (HL-07185) from the National Heart, Lung, and Blood Institute.

Received for publication February 4, 2006. Accepted for publication April 1, 2006.

References

1. Fahy, JV (2003) Airway mucus and the mucociliary system. Adkinson, NF Bochner, BS Yunginger, JWet al eds. Allergy principles and practice ,741-757 Mosby. Philadelphia, PA:
2. Vestbo, J, Hogg, JC Convergence of the epidemiology and pathology of COPD. Thorax 2006;61,86-88[Abstract/Free Full Text]
3. Thurlbeck, WM, Angus, GE The relationship between emphysema and chronic bronchitis as assessed morphologically. Am Rev Respir Dis 1963;87,815-819[ISI][Medline]
4. Reid, LM Pathology of chronic bronchitis. Lancet 1954;266,274-278[Medline]
5. Saetta, M, Turato, G, Baraldo, S, et al Goblet cell hyperplasia and epithelial inflammation in peripheral airways of smokers with both symptoms of chronic bronchitis and chronic airflow limitation. Am J Respir Crit Care Med 2000;161,1016-1021[Abstract/Free Full Text]
6. Saetta, M, Turato, G, Facchini, FM, et al Inflammatory cells in the bronchial glands of smokers with chronic bronchitis. Am J Respir Crit Care Med 1997;156,1633-1639[Abstract/Free Full Text]
7. Fletcher, CM, Peto, R, Tinker, CM, et al The natural history of chronic bronchitis and emphysema. 1976 Oxford University Press. New York, NY:
8. Vestbo, J, Prescott, E, Lange, P Association of chronic mucus hypersecretion with FEV₁ decline and chronic obstructive pulmonary disease morbidity: Copenhagen City Heart Study Group. Am J Respir Crit Care Med 1996;153,1530-1535[Abstract]
9. Banerjee, D, Khair, OA, Honeybourne, D Impact of sputum bacteria on airway inflammation and health status in clinical stable COPD. Eur Respir J 2004;23,685-691[Abstract/Free Full Text]
10. Donaldson, GC, Seemungal, TA, Bhowmik, A, et al Relationship between exacerbation frequency and lung function decline in chronic obstructive pulmonary disease. Thorax 2002;57,847-852[Abstract/Free Full Text]
11. Anthonisen, NR The British hypothesis revisited. Eur Respir J 2004;23,657-658[Free Full Text]
12. Jeffery, PK Remodeling in asthma and chronic obstructive lung disease. Am J Respir Crit Care Med 2001;164,S28-S38[Abstract/Free Full Text]
13. O’Donnell, RA, Richter, A, Ward, J, et al Expression of ErbB receptors and mucins in the airways of long term current smokers. Thorax 2004;59,1032-1040[Abstract/Free Full Text]
14. Bolender, RP, Hyde, DM, Dehoff, RT Lung morphometry: a new generation of tools and experiments for organ, tissue, cell, and molecular biology. Am J Physiol 1993;265,L521-L548
15. Ferrando, RE, Nyengaard, JR, Hays, SR, et al Applying stereology to measure thickness of the basement membrane zone in bronchial biopsy specimens. J Allergy Clin Immunol 2003;112,1243-1245[CrossRef][ISI][Medline]
16. Hays, SR, Woodruff, PG, Khashayar, R, et al Allergen challenge causes inflammation but not goblet cell degranulation in asthmatic subjects. J Allergy Clin Immunol 2001;108,784-790[CrossRef][ISI][Medline]
17. Woodruff, PG, Dolganov, GM, Ferrando, RE, et al Hyperplasia of smooth muscle in mild to moderate asthma without changes in cell size or gene expression. Am J Respir Crit Care Med 2004;169,1001-1006[Abstract/Free Full Text]
18. National Heart, Lung, and Blood Institute, World Health Organization. Global strategy for the diagnosis, management, and prevention of COPD: NHLBI/WHO Workshop; updated 2004. Available at: http://www.evimed.ch/Downloadables/gold_guidelines.pdf. Accessed January 5, 2006
19. Dolganov, GM, Woodruff, PG, Novikov, AA, et al A novel method of gene transcript profiling in airway biopsy homogenates reveals increased expression of a Na+-K+-Cl- cotransporter (NKCC1) in asthmatic subjects. Genome Res 2001;11,1473-1483[Abstract/Free Full Text]
20. Sidak, Z Rectangular confidence regions for the means of multivariate normal distributions. J Am Stat Assoc 1967;62,626-633[CrossRef]
21. Nagai, A, West, WW, Thurlbeck, WM The National Institutes of Health Intermittent Positive-Pressure Breathing Trial: pathology studies; II. Correlation between morphologic findings, clinical findings, and evidence of expiratory air-flow obstruction. Am Rev Respir Dis 1985;132,946-953[ISI][Medline]
22. Hogg, JC, Chu, F, Utokaparch, S, et al The nature of small-airway obstruction in chronic obstructive pulmonary disease. N Engl J Med 2004;350,2645-2653[Abstract/Free Full Text]
23. Hardie, WD, Le Cras, TD, Jiang, K, et al Conditional expression of transforming growth factor- in adult mouse lung causes pulmonary fibrosis. Am J Physiol Lung Cell Mol Physiol 2004;286,L741-L749[Abstract/Free Full Text]
24. De Haller, R, Reid, L Adult chronic bronchitis: morphology, histochemistry and vascularisation of the bronchial mucous glands. Med Thorac 1965;22,549-567[ISI][Medline]
25. Anthonisen, NR, Connett, JE, Kiley, JP, et al Effects of smoking intervention and the use of an inhaled anticholinergic bronchodilator on the rate of decline of FEV₁: the Lung Health Study. JAMA 1994;272,1497-1505[Abstract]
26. Swan, GE, Hodgkin, JE, Roby, T, et al Reversibility of airways injury over a 12-month period following smoking cessation. Chest 1992;101,607-612[Abstract/Free Full Text]

This article has been cited by other articles:

				S. Siddiqui, F. Hollins, S. Saha, and C. E. Brightling Inflammatory cell microlocalisation and airway dysfunction: cause and effect? Eur. Respir. J., December 1, 2007; 30(6): 1043 - 1056. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) Free Online supplemental file Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Add to My Personal Article Archive Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Innes, A. L. Articles by Fahy, J. V. Search for Related Content PubMed PubMed Citation Articles by Innes, A. L. Articles by Fahy, J. V.