Morphometry of small airways in smokers and its relationship to emphysema type and hyperresponsiveness

Panlobular emphysema is associated with COPD disease severity: A study of emphysema subtype by computed tomography

BACKGROUND

Computed tomography has the potential to inform COPD prognosis. We sought to determine associations of emphysema phenotype with clinical parameters including lung function, inflammatory markers, and quality of life.

METHODS

Participants of this single-center observational cohort (n = 83) were 40-80 years old, had ≥10 pack-year smoking, and a diagnosis of COPD confirmed by spirometry. All participants had available historic chest CT scans which were systematically reviewed by a single expert radiologist and scored for emphysema subtype, extent, and distribution. Associations between radiographic findings and clinical parameters were determined.

RESULTS

Median age of participants was 72 years, median smoking 40 pack-years, and median FEV₁ 59% predicted. 84% of the participants had radiographic emphysema. Of those, 26% had panlobular emphysema (PLE), 68% centrilobular emphysema (CLE), and 6% paraseptal emphysema (PSE). As compared to the participants with no radiographic emphysema, the presence of PLE-dominant emphysema was associated with a lower BMI (P = 0.012) and greater extent of emphysema (P = 0.014). After adjusting for age, sex, and pack-years smoking history, PLE was associated with greater airflow obstruction by FEV₁% (48% vs 71%, P = 0.005), greater symptom burden by CAT score (18 vs 9, P = 0.015), worse quality of life by SGRQ score (43 vs 22, P = 0.025), and more systemic inflammation by erythrocyte sedimentation rate (P = 0.001). CLE- or PSE-dominant emphysema were not similarly associated with clinical features or symptom burden.

CONCLUSIONS

The presence of PLE-dominant emphysema was associated with greater extent of emphysema, greater airflow obstruction, increased respiratory symptoms, worse quality of life, and systemic inflammation. Further investigation is indicated to explore the pathogenesis of the PLE phenotype and the prognostic and treatment implications of PLE.

The Role of ABC Transporters in Lipid Metabolism and the Comorbid Course of Chronic Obstructive Pulmonary Disease and Atherosclerosis

Chronic obstructive pulmonary disease (COPD) ranks among the leading causes of morbidity and mortality worldwide. COPD rarely occurs in isolation and is often combined with various diseases. It is considered that systemic inflammation underlies the comorbid course of COPD. The data obtained in recent years have shown the importance of violations of the cross-links of lipid metabolism and the immune response, which are links in the pathogenesis of both COPD and atherosclerosis. The role of lipid metabolism disorders in the pathogenesis of the comorbid course of COPD and atherosclerosis and the participation of ATP-binding cassette (ABC) transporters in these processes is discussed in this article. It is known that about 20 representatives of a large family of ABC transporters provide lipid homeostasis of cells by moving lipids inside the cell and in its plasma membrane, as well as removing lipids from the cell. It was shown that some representatives of the ABC-transporter family are involved in various links of the pathogenesis of COPD and atherosclerosis, which can determine their comorbid course.

A critical role for ABC transporters in persistent lung inflammation in the development of emphysema after smoke exposure

Macrophage infiltration is common to both emphysema and atherosclerosis, and cigarette smoke down-regulates the macrophage cholesterol efflux transporter ATP binding cassette (ABC)A1. This decreased cholesterol efflux results in lipid-laden macrophages. We hypothesize that cigarette smoke adversely affects cholesterol transport via an ABCA1-dependent mechanism in macrophages, enhancing TLR4/myeloid differentiation primary response gene 88 (Myd88) signaling and resulting in matrix metalloproteinase (MMP) up-regulation and exacerbation of pulmonary inflammation. ABCA1 is significantly down-regulated in the lung upon smoke exposure conditions. Macrophages exposed to cigarette smoke in vivo and in vitro exhibit impaired cholesterol efflux correlating with significantly decreased ABCA1 expression, up-regulation of the TLR4/Myd88 pathway, and downstream MMP-9 and MMP-13 expression. Treatment with liver X receptor (LXR) agonist restores ABCA1 expression after short-term smoke exposure and attenuates the inflammatory response; after long-term smoke exposure, there is also attenuated physiologic and morphologic changes of emphysema. In vitro, treatment with LXR agonist decreases macrophage inflammatory activation in wild-type but not ABCA1 knockout mice, suggesting an ABCA1-dependent mechanism of action. These studies demonstrate an important association between cigarette smoke exposure and cholesterol-mediated pathways in the macrophage inflammatory response. Modulation of these pathways through manipulation of ABCA1 activity effectively blocks cigarette smoke-induced inflammation and provides a potential novel therapeutic approach for the treatment of chronic obstructive pulmonary disease.-Sonett, J., Goldklang, M., Sklepkiewicz, P., Gerber, A., Trischler, J., Zelonina, T., Westerterp, M., Lemaître, V., Okada, V., D'Armiento, J. A critical role for ABC transporters in persistent lung inflammation in the development of emphysema after smoke exposure.

Analysis of airway pathology in COPD using a combination of computed tomography, micro-computed tomography and histology

The small conducting airways are the major site of obstruction in chronic obstructive pulmonary disease (COPD). This study examined small airway pathology using a novel combination of multidetector row computed tomography (MDCT), micro-computed tomography (microCT) and histology.Airway branches visible on specimen MDCT were counted and the dimensions of the third- to fifth-generation airways were computed, while the terminal bronchioles (designated TB), preterminal bronchioles (TB-1) and pre-preterminal bronchioles (TB-2) were examined with microCT and histology in eight explanted lungs with end-stage COPD and seven unused donor lungs that served as controls.On MDCT, COPD lungs showed a decrease in the number of 2-2.5 mm diameter airways and the lumen area of fifth-generation airways, while on microCT there was a reduction in the number of terminal bronchioles as well as a decrease in the luminal areas, wall volumes and alveolar attachments to the walls of TB, TB-1 and TB-2 bronchioles. The combination of microCT and histology showed increased B-cell infiltration into the walls of TB-1 and TB-2 bronchioles, and this change was correlated with a reduced number of alveolar attachments in COPD.Small airways disease extends from 2 mm diameter airways to the terminal bronchioles in COPD. Destruction of alveolar attachments may be driven by a B-cell-mediated immune response in the preterminal bronchioles.

[Morphological changes in the respiratory organs in chronic obstructive pulmonary disease]

The basis for airway remoldeling in patients with chronic obstructive pulmonary disease (COPD) is tissue changes contributing to thickening of the walls of the airway and its obstruction. As the disease becomes severer, there are increases in mucosal metaplasia, submucosal hypertrophy, peribronchial fibrosis, and airway smooth muscle mass. Drug therapy for COPD does not virtually lead to regression of airway obstruction, except when eosinophilia is present.

Risk factors and early origins of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease is mainly a smoking-related disorder and affects millions of people worldwide, with a large effect on individual patients and society as a whole. Although the disease becomes clinically apparent around the age of 40-50 years, its origins can begin very early in life. Different risk factors in very early life--ie, in utero and during early childhood--drive the development of clinically apparent chronic obstructive pulmonary disease in later life. In discussions of which risk factors drive chronic obstructive pulmonary disease, it is important to realise that the disease is very heterogeneous and at present is largely diagnosed by lung function only. In this Review, we will discuss the evidence for risk factors for the various phenotypes of chronic obstructive pulmonary disease during different stages of life.

Chronic obstructive pulmonary disease

COPD is characterized by airflow limitation that is not fully reversible. The morphological basis for airflow obstruction results from a varying combination of obstructive changes in peripheral conducting airways and destructive changes in respiratory bronchioles, alveolar ducts, and alveoli. A reduction of vascularity within the alveolar septa has been reported in emphysema. Typical physiological changes reflect these structural abnormalities. Spirometry documents airflow obstruction when the FEV1/FVC ratio is reduced below the lower limit of normality, although in early disease stages FEV1 and airway conductance are not affected. Current guidelines recommend testing for bronchoreversibility at least once and the postbronchodilator FEV1/FVC be used for COPD diagnosis; the nature of bronchodilator response remains controversial, however. One major functional consequence of altered lung mechanics is lung hyperinflation. FRC may increase as a result of static or dynamic mechanisms, or both. The link between dynamic lung hyperinflation and expiratory flow limitation during tidal breathing has been demonstrated. Hyperinflation may increase the load on inspiratory muscles, with resulting length adaptation of diaphragm. Reduction of exercise tolerance is frequently noted, with compelling evidence that breathlessness and altered lung mechanics play a major role. Lung function measurements have been traditionally used as prognostic indices and to monitor disease progression; FEV1 has been most widely used. An increase in FVC is also considered as proof of bronchodilatation. Decades of work has provided insight into the histological, functional, and biological features of COPD. This has provided a clearer understanding of important pathobiological processes and has provided additional therapeutic options.

Effect of cold-dryness on pulmonary and immunologic function in chronic obstructive pulmonary disease model rats

OBJECTIVE

To study the effects of cold-dryness on pulmonary and immunologic function of peripheral T-lymphocytes in chronic obstructive pulmonary disease (COPD) model rats, and to provide references for the prevention and treatment of cold-dryness COPD in the Xinjiang region.

METHODS

The COPD model was established with an elastase drip into the trachea combined with smoking. The cold-dryness COPD model was developed by stressing with a cold-dry environment. Success of the model was determined by observation of pathologic lung sections. Rats were sacrificed by exsanguination from the femoral artery and changes of peripheral blood CD4+, CD8+, and CD4+/CD8+ were detected by flow cytometry. Data were analyzed with SAS 11.5 statistical software.

RESULTS

On the ninetieth day after ending the experiment, Peak expiratory flow in the cold-dryness COPD group was lower than that in the COPD and normal control groups (P < 0.01). The time of inspiration in the cold-dryness COPD group was higher than that in the COPD and normal groups (P < 0.05). Time of expiration (Te) in the cold-dryness COPD group was higher than that in the COPD and normal groups (P < 0.01). 50% tidal volume expiratory flow (EF50) in the cold-dryness COPD group was lower than that in the COPD and normal groups (P < 0.01), and EF50 in the COPD group was lower than that in the normal group (P < 0.05). CD4+ content of peripheral blood in the cold-dryness COPD group was lower than that in the COPD and the normal groups (P < 0.05). CD8+ content in the cold-dryness COPD and COPD groups was higher than that in the normal control group (P < 0.01), and CD8+ content in the cold-dryness COPD group was higher than that in the COPD group (P < 0.01). CD4+/CD8+ in the cold-dryness COPD group and the COPD group was lower than that in the normal control group (P < 0.01), and CD4+/CD8+ in the cold-dryness COPD group was lower than that in the COPD group (P < 0.05).

CONCLUSION

In the cold-dryness COPD model, CD8+ increased and CD4+/CD8+ decreased. Moreover, cold-dryness may aggravate this state. The effects of cold-dryness on pulmonary function mainly manifested as prolongation of Te and decrease of EF50, which could be one of causes of cold-dryness environment in the northwest of China leading to COPD with region characteristics.

Asthma and chronic obstructive pulmonary disease: similarities and differences

Asthma and COPD are both heterogeneous lung diseases including many different phenotypes. The classical asthma and COPD phenotypes are easy to discern because they reflect extremes of a phenotypical spectrum. Thus asthma in childhood and COPD in smokers have their own phenotypic expression with underlying pathophysiological mechanisms that differ importantly. In older adults, asthma and COPD are more difficult to differentiate and there exists a bronchodilator response in most but not all patients with asthma and persistent airway obstruction in most but not all patients with COPD where even up to 50% have been reported to have some bronchodilator response as assessed with FEV1. Airway obstruction is generated in the large and small airways both in asthma and COPD, and this small airway obstruction is located more proximally in asthma, yet is found more distally in severe and older individuals with asthma, comparable to COPD. Though the underlying inflammation and remodelling processes in asthma and COPD are different in their extreme phenotypes, there are overlap phenotypes with eosinophilic inflammation even in stable COPD and neutrophilic inflammation in longstanding and severe asthma.

Accurate measurement of small airways on low-dose thoracic CT scans in smokers

BACKGROUND

Partial volume averaging and tilt relative to the scan plane on transverse images limit the accuracy of airway wall thickness measurements on CT scan, confounding assessment of the relationship between airway remodeling and clinical status in COPD. The purpose of this study was to assess the effect of partial volume averaging and tilt corrections on airway wall thickness measurement accuracy and on relationships between airway wall thickening and clinical status in COPD.

METHODS

Airway wall thickness measurements in 80 heavy smokers were obtained on transverse images from low-dose CT scan using the open-source program Airway Inspector. Measurements were corrected for partial volume averaging and tilt effects using an attenuation- and geometry-based algorithm and compared with functional status.

RESULTS

The algorithm reduced wall thickness measurements of smaller airways to a greater degree than larger airways, increasing the overall range. When restricted to analyses of airways with an inner diameter < 3.0 mm, for a theoretical airway of 2.0 mm inner diameter, the wall thickness decreased from 1.07 ± 0.07 to 0.29 ± 0.10 mm, and the square root of the wall area decreased from 3.34 ± 0.15 to 1.58 ± 0.29 mm, comparable to histologic measurement studies. Corrected measurements had higher correlation with FEV₁, differed more between BMI, airflow obstruction, dyspnea, and exercise capacity (BODE) index scores, and explained a greater proportion of FEV1 variability in multivariate models.

CONCLUSIONS

Correcting for partial volume averaging improves accuracy of airway wall thickness estimation, allowing direct measurement of the small airways to better define their role in COPD.

Association of genes of protease-antiprotease balance pathway to lung function and emphysema subtypes

Background

The imbalance between proteases and antiproteases has been proposed to participate to the pathogenesis of chronic obstructive pulmonary disease (COPD) and emphysema. Gene level variation in different metalloproteinases, metalloproteinase inhibitors, and cytokines affecting them may contribute to this imbalance and destruction of the lung parenchyma. We investigated whether polymorphisms in selected protease-antiprotease balance pathway genes predispose to different emphysema subtypes (centrilobular, paraseptal, panlobular, and bullae) and airflow limitation among Finnish construction workers.

Methods

Eleven single nucleotide polymorphisms (SNPs) from seven genes (GC: rs7041 and rs4588; MMP1: rs1799750; MMP9: rs3918242; MMP12: rs652438; TIMP2: rs2277698; TNF: rs1799724 and rs1800629; TGFB1: rs1800469, rs1800470, and rs2241718) were analyzed from 951 clinically and radiologically characterized construction workers. The genotype and haplotype data was compared to different emphysematous signs confirmed with high resolution computed tomography (HRCT), forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), and maximal expiratory flow at 50% of FVC (MEF50) by using linear and logistic regression analyses, adjusted for potential confounders.

Results

The TIMP2 rs2277698 SNP was associated with overall (p = 0.022) and paraseptal (p = 0.010) emphysema, as well as with FEV₁/FVC ratio (p = 0.035) and MEF50 (p = 0.008). The TGFB1 rs2241718 and MMP9 rs3918242 SNPs were associated with centrilobular emphysema (p = 0.022 and p = 0.008), and the TNF rs1800629 SNP with paraseptal emphysema (p = 0.017). In stratified analysis, individuals with at least one TIMP2 rs2277698 or TNF rs1800629 variant allele were found to be at around two-fold risk for pathological paraseptal changes (OR 1.94, 95% CI 1.14-3.30; OR 2.10, 95% CI 1.24-3.56). On the contrary, the risk for pathological centrilobular changes was halved for individuals with at least one MMP9 rs3918242 (OR 0.51, 95% CI 0.30-0.86) or TGFB1 rs2241718 (OR 0.53, 95% CI 0.30-0.90) variant allele, or TGFB1 rs1800469-rs1800470 AT-haplotype (OR 0.55, 95% CI 0.33-0.93). MEF50, in turn, was significantly reduced among individuals with at least one TIMP2 rs2277698 variant allele (p = 0.011).

Conclusion

Our findings strengthen the hypothesis of the importance of protease-antiprotease balance in pathogenesis of emphysema and shed light on the aetiology of different emphysema subtypes by associating MMP9 and TGFB1 to centrilobular emphysema, and TIMP2 and TNF to paraseptal emphysema and/or airflow obstruction.

Mast cell infiltration discriminates between histopathological phenotypes of chronic obstructive pulmonary disease

RATIONALE

COPD is a complex disease with heterogeneous manifestations. Attempts have been made to define different phenotypes that could guide toward better disease understanding. We described before that smokers can develop either panlobular (PLE) or centrilobular emphysema (CLE). The latter has worse small airways remodeling and narrowing, which account for the airflow obstruction similar to asthma.

OBJECTIVES

Because of the small airways involvement in CLE similar to asthma, we hypothesized a role for mast cells in CLE but not in PLE. Hence, we investigated mast cell infiltration, along with overall inflammation, and their relation with hyperreactivity and emphysema type in COPD.

METHODS

We studied lung function, emphysema type, mast cells, and overall inflammation in small airways and alveolar walls, along with alveolar wall thickening in 67 subjects undergoing lung resection (59 smokers, 8 nonsmokers).

MEASUREMENTS AND MAIN RESULTS

Twenty-seven smokers had CLE, 24 had PLE, and 8 had no emphysema. Mast cells were significantly increased in CLE compared with PLE and control subjects. Especially relevant was the mast cell increase in airway smooth muscle in CLE, which related significantly to airway hyperreactivity. CD4(+)T cells, neutrophils, and macrophages, but not eosinophils and CD8(+)T cells, were significantly higher in CLE than PLE. Alveolar wall thickness was increased in all smokers, but significantly more in CLE.

CONCLUSIONS

The pathological phenotypes of COPD CLE and PLE show important differences in their overall inflammation with a protagonism of mast cells, which are related to airway reactivity. These findings highlight the distinctness of these COPD phenotypes and the role of mast cells in the pathophysiology of COPD.

[Structural abnormalities and inflammation in COPD: a focus on small airways]

Chronic obstructive pulmonary disease (COPD) is characterized by poorly reversible airflow limitation associated with airway remodelling and inflammation of both large and small airways. The site of airflow obstruction in COPD is located in the small airways, justifying a focus on this compartment. The structural abnormalities that are found in bronchioles with a diameter less than 2mm are characterized by increased airway wall thickness with peribronchial fibrosis, and by luminal obstruction by mucous exudates. Destruction of alveolar walls, the hallmark of emphysema, may be related to protease-antiprotease imbalance, and to mechanisms involving apoptosis, senescence, and autoimmunity. Cigarette smoke inhalation triggers the recruitment of innate immune cells (neutrophils and macrophages) and putatively adaptive immunity mediated via T and B lymphocytes and lymphoid follicles in the small airways. These data suggest a potential role for therapies that can target remodelling and inflammation in the small airways of patients with COPD.

Does nasal hair (vibrissae) density affect the risk of developing asthma in patients with seasonal rhinitis?

BACKGROUND

Large particles entering the nose are collected by nasal hair present in the anterior nares. Increased hair density provides an improvement in the filtering efficiency of the nose, while reduced amounts of nasal hair cause a decrease in its efficiency. The amount of nasal hair can vary between individuals, which can make a difference in the filtering efficiency of the nose. Reduced filter function of the nose leads to increased exposure of the airways to allergens. The aim of this study was to determine the effect of nasal hair density on the risk of developing asthma in seasonal rhinitis (SR) patients.

METHODS

A standard questionnaire was filled in, and physical examination and allergy tests were performed in 233 patients. Patients were divided into 3 groups according to the amount of nasal hair [few (few or none), moderate and many]. The association between asthma and nasal hair density was assessed.

RESULTS

Asthma was detected in 75 patients (32.2%), and of these, 45 (60%) also had pollen asthma. The rate of asthma was 44.7, 26.2 and 16.7% in the few, moderate and many groups, respectively (p = 0.002). Few nasal hairs significantly increased the risk of developing asthma [odds ratio (95% confidence interval): few, reference; moderate, 0.41 (0.21-0.78); many, 0.19 (0.06-0.55); p = 0.002].

CONCLUSION

Our findings suggest that the amount of nasal hair providing a nose filtration function has a protective effect on the risk of developing asthma in SR patients. To the best of our knowledge, this is the first report on this subject in the literature.

Small airway pathology and bronchoreversibility in advanced emphysema

BACKGROUND

Poorly reversible airflow obstruction is a hallmark feature of chronic obstructive pulmonary disease (COPD). However, some COPD patients demonstrate significant bronchodilator reversibility (BDR). The pathologic features associated with the presence or absence of this phenomenon are not known.

METHODS

We analyzed 67 patients with advanced upper lobe predominant emphysema who underwent lung volume reduction surgery and divided them into 2 groups: the reversible group [BD(+)] had a >12% and >200 mL increase in FEV(1) or FVC with bronchodilator; the irreversible group [BD(-)] had a <or=12% and <or=20 mL increase in FEV(1) and FVC. We measured the epithelial height (EH) and areas of epithelium (EA), subepithelium (SEA), smooth muscle (SMWA), and total wall (TWA) of the small airways (<2 mm in internal diameter) in the resected specimens, and adjusted these measurements for basement membrane area (BMA) or perimeter (BMP).

RESULTS

Despite similar baseline characteristics, the BD(+) group had a smaller EH (0.036 mm vs. 0.042 mm, p = 0.005) and EH/BMP (0.012 vs. 0.014, p = 0.007), and a greater SMWA/BMA (0.491 vs. 0.430, p = 0.034) compared to the BD(-) group. In addition, EA trended to be smaller in the BD(+) group when compared to the BD(-) group (0.160 mm(2) vs. 0.184 mm(2), p = 0.06). In a subset of patients with consistent patterns of BDR on serial testing, the BD(+) group had greater SMWA/BMA (0.518 vs. 0.433, p = 0.049) and TWA/BMA (1.405 vs. 1.266, p = 0.036) compared to the BD(-) group.

CONCLUSIONS

Small airway smooth muscle mass may play a role in determining BDR in severe emphysema.

Airway responsiveness to indirect challenges in COPD

Patients with chronic obstructive pulmonary disease (COPD) demonstrate airway hyperresponsiveness to a number of indirect stimuli. Hyperresponsiveness to cold air hyperventilation, exercise, and drugs like propranalol and methoxamine seem to be able to distinguish patients with COPD from those with asthma, whereas hyperresponsiveness to stimuli like adenosine 5-monophosphate (AMP) and hypertonic saline seem unable to do so. The relationship of airway responsiveness to indirect stimuli and airway inflammation has received little study. The clinical relevance of hyperresponsiveness to an indirect challenge, including the impact on the natural history, relation to types of bronchitis, baseline airway calibre, and response to treatment need to be studied.

Moraxella catarrhalis-specific Th1 cells in BAL fluids of chronic obstructive pulmonary disease patients

In chronic obstructive pulmonary disease (COPD) patients airway mucosa is infiltrated by macrophages and T lymphocytes, potentially reactive to pathogens. We studied the antigen-specificity and the effector functions of in vivo activated T lymphocytes isolated from BAL (Bronchoalveolar lavage) of 5 Moraxella catarrhalis (Mc)-infected and 5 Mc-non-infected COPD patients. Mc-specific T cells were detected only in BAL or peripheral blood of Moraxella catarrhalis-infected patients. The majority of BAL Mc-specific T cells expressed the T helper type 1 (Th1) cytokine profile with high cytotoxic and pro-apoptotic activity. Upon antigen stimulation, all Mc-specific T clones were able to help the immunoglobulin production by autologous B cells and the MMP (Matrix MetalloProteinase)-12 activity by monocytes. Our results suggest a role for Th1-driven response to Moraxella catarrhalis in the genesis of COPD.

Imaging of pulmonary emphysema: a pictorial review

The term 'emphysema' is generally used in a morphological sense, and therefore imaging modalities have an important role in diagnosing this disease. In particular, high resolution computed tomography (HRCT) is a reliable tool for demonstrating the pathology of emphysema, even in subtle changes within secondary pulmonary lobules. Generally, pulmonary emphysema is classified into three types related to the lobular anatomy: centrilobular emphysema, panlobular emphysema, and paraseptal emphysema. In this pictorial review, we discuss the radiological--pathological correlation in each type of pulmonary emphysema. HRCT of early centrilobular emphysema shows an evenly distributed centrilobular tiny areas of low attenuation with ill-defined borders. With enlargement of the dilated airspace, the surrounding lung parenchyma is compressed, which enables observation of a clear border between the emphysematous area and the normal lung. Because the disease progresses from the centrilobular portion, normal lung parenchyma in the perilobular portion tends to be preserved, even in a case of far-advanced pulmonary emphysema. In panlobular emphysema, HRCT shows either panlobular low attenuation or ill-defined diffuse low attenuation of the lung. Paraseptal emphysema is characterized by subpleural well-defined cystic spaces. Recent topics related to imaging of pulmonary emphysema will also be discussed, including morphometry of the airway in cases of chronic obstructive pulmonary disease, combined pulmonary fibrosis and pulmonary emphysema, and bronchogenic carcinoma associated with bullous lung disease.

Distal airways in mice exposed to cigarette smoke: Nrf2-regulated genes are increased in Clara cells

Cigarette smoke (CS) is the main risk factor for chronic obstructive pulmonary disease (COPD). Terminal bronchioles are critical zones in the pathophysiology of COPD, but little is known about the cellular and molecular changes that occur in cells lining terminal bronchioles in response to CS. We subjected C57BL/6 mice to CS (6 d/wk, up to 6 mo), looked for morphologic changes lining the terminal bronchioles, and used laser capture microdissection to selectively isolate cells in terminal bronchioles to study gene expression. Morphologic and immunohistochemical analyses showed that Clara cell predominance remained despite 6 months of CS exposure. Since Clara cells have a role in protection against oxidative stress, we focused on the expression of antioxidant/detoxification genes using microarray analysis. Of the 35 antioxidant/detoxification genes with at least 2.5-fold increased expression in response to 6 months of CS exposure, 21 were NF-E2-related factor 2 (Nrf2)-regulated genes. Among these were cytochrome P450 1b1, glutathione reductase, thioredoxin reductase, and members of the glutathione S-transferase family, as well as Nrf2 itself. In vitro studies using immortalized murine Clara cells (C22) showed that CS induced the stabilization and nuclear translocation of Nrf2, which correlated with the induction of antioxidant and detoxification genes. Furthermore, decreasing Nrf2 expression by siRNA resulted in a corresponding decrease in CS-induced expression of several antioxidant and detoxification genes by C22 cells. These data suggest that the protective response by Clara cells to CS exposure is predominantly regulated by the transcription factor Nrf2.

Killer cells in chronic obstructive pulmonary disease

COPD (chronic obstructive pulmonary disease) is a treatable and preventable disease state, characterized by progressive airflow limitation that is not fully reversible. It is a current and growing cause of mortality and morbidity worldwide, with the WHO (World Health Organization) projecting that total deaths attributed to COPD will increase by more than 30% in the next 10 years. The pathological hallmarks of COPD are destruction of the lung parenchyma (pulmonary emphysema), inflammation of the central airways (chronic bronchitis) and inflammation of the peripheral airways (respiratory bronchiolitis). The destructive changes and tissue remodelling observed in COPD are a result of complex interactions between cells of the innate and adaptive immune systems. The focus of the present review is directed towards the role of CD8(+) T-lymphocytes, NK (natural killer) cells and NKT cells (NK T-cells). These three classes of killer cell could all play an important part in the pathogenesis of COPD. The observed damage to the pulmonary tissue could be caused in three ways: (i) direct cytotoxic effect against the lung epithelium mediated by the activities of perforin and granzymes, (ii) FasL (Fas ligand)-induced apoptosis and/or (iii) cytokine and chemokine release. The present review considers the role of these killer cells in COPD.

Molecular pathogenesis of emphysema

Emphysema is one manifestation of a group of chronic, obstructive, and frequently progressive destructive lung diseases. Cigarette smoking and air pollution are the main causes of emphysema in humans, and cigarette smoking causes emphysema in rodents. This review examines the concept of a homeostatically active lung structure maintenance program that, when attacked by proteases and oxidants, leads to the loss of alveolar septal cells and airspace enlargement. Inflammatory and noninflammatory mechanisms of disease pathogenesis, as well as the role of the innate and adaptive immune systems, are being explored in genetically altered animals and in exposure models of this disease. These recent scientific advances support a model whereby alveolar destruction resulting from a coalescence of mechanical forces, such as hyperinflation, and more recently recognized cellular and molecular events, including apoptosis, cellular senescence, and failed lung tissue repair, produces the clinically recognized syndrome of emphysema.

The association between small airway obstruction and emphysema phenotypes in COPD

BACKGROUND

Airflow limitation in COPD is due to a variable combination of small airway obstruction and centrilobular emphysema (CLE) and/or panlobular emphysema (PLE), but the relationship between these three different phenotypes is poorly understood. This study compares the severity of small airway obstruction in both forms of emphysema and determines its relationship with FEV(1).

METHODS

We compared the lung histology of nonsmoking control subjects without emphysema (n = 10) to that of patients with CLE (n = 30) and PLE with (n = 8) and without alpha(1)-antitrypsin (AAT) deficiency (n = 11). The degree of airspace enlargement was measured using the mean interalveolar wall distance (IAWD) [mean linear intercept, Lm], and the evenness of airspace destruction was assessed by the coefficient of variation (CV) of the IAWD. The severity of small airway obstruction was determined by dividing total wall area by the length of the basement membrane to obtain wall thickness.

RESULTS

Lm was greater in all three subgroups of emphysema than in control subjects, and in AAT deficiency than in PLE or CLE. The CV of IAWD was greater in AAT deficiency and CLE than in control subjects and in CLE than in AAT deficiency or PLE. Although small airway wall thickness was greater in CLE and PLE with AAT deficiency than in control subjects, the association between wall thickness and both Lm and FEV(1) was observed only in CLE.

CONCLUSIONS

Small airway wall thickening occurs in CLE and PLE with AAT deficiency but is more closely associated with degree of emphysema and airflow limitation in CLE.

A disintegrin and metalloprotease 33 and chronic obstructive pulmonary disease pathophysiology

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a respiratory disorder with increasing prevalence and mortality. It is associated with airway obstruction, increased airway hyper-responsiveness (AHR), and ongoing airway and lung inflammation dominated by CD8 lymphocytes and neutrophils. Single-nucleotide polymorphisms (SNPs) in a disintegrin and metalloprotease 33 (ADAM33) gene have been associated with AHR and COPD.

OBJECTIVE

To assess whether SNPs in ADAM33 are associated with the severity of AHR and airway inflammation in COPD.

METHODS

Eight SNPs in ADAM33 (F+1, Q-1, S_1, S_2, ST+5, T_1, T_2, V_4) were genotyped in 111 patients with COPD (96 males, 69 current smokers, mean (standard deviation (SD)), aged 62 (8) years, median pack-years 42 (IQR 31-55), mean postbronchodilator forced expiratory volume in 1 s (FEV(1))% predicted 63 (9). Provocative concentration of methacholine causing a decrease in FEV(1) of 20% (PC(20) methacholine), sputum and bronchial biopsies were collected.

RESULTS

Patients with the ST+5 AA genotype had more severe AHR, higher numbers of sputum inflammatory cells and CD8 cells in bronchial biopsies than patients with the GG genotype (p = 0.03, 0.05 and 0.01, respectively). CD8 cell numbers were lower in patients carrying the minor allele of SNP T_1 and T_2, and homozygotic minor variants of SNP S_2 compared with the wild type (p = 0.02, 0.01 and 0.02, respectively).

CONCLUSIONS

This is the first study revealing that SNPs in a gene that confers susceptibility to COPD in the general population-that is, ADAM33-are associated with AHR and airway inflammation in COPD. These findings constitute an important step forward in linking gene polymorphisms with COPD pathophysiology, thereby possibly contributing to better treatments for this progressive and disabling disease in the future.

Light cigarette smoke-induced emphysema and NFkappaB activation in mouse lung

Light cigarette (LC) exposure is supposed to be less hazardous with a decreased incidence of cancer and tobacco-associated diseases. C57BL/6 mouse groups were subjected to smoke from 3, 6 or 12 LC for 60 days and compared with mice exposed to ambient air (EAA) in order to study lung injury by morphometrical and biochemical methods. Bronchoalveolar lavage (BAL) analysis and histology and stereology were performed. Tissue from the right lung was used for measuring thiobarbituric acid reactive substances (TBARS) and Western blot analysis. One way anova was performed followed by the Student-Newman Keuls post-test (P < 0.05). The cellular content of BAL was 95% alveolar macrophages in all groups except in mice exposed to 3 LC, where 23% neutrophils were observed. Emphysema was not observed in three and 6 LC, but it was found in 12 LC parallel to increased volume density (Vv) of airspaces from 61.0 +/- 0.6 (EAA) to 80.9 +/- 1.0 (12 LC) and decreased Vv of elastic fibres from 17.8 +/- 0.9 (EAA) to 11.8 +/- 0.6 (12 LC). All exposed groups to LC showed low TBARS levels compared with mice EAA. Lung tissue from animals exposed to 12 LC showed decreased tissue inhibitor of metalloprotease-2 and increased matrix metalloprotease-12 detection, which suggests an imbalance in extracellular matrix (ECM). Increased tumour necrosis factor-alpha and nuclear factor-kappaB detection were observed in exposed groups to LC when compared with mice EAA. The data suggest that LC is so dangerous to lungs as full-flavour cigarettes inducing ECM imbalance and emphysema.

Inflammatory cells in the airways in COPD

Airway inflammation is central to the pathogenesis of both airway remodelling and parenchymal destruction in chronic obstructive pulmonary disease (COPD). Neutrophils, macrophages, and CD8+ T lymphocytes have been implicated in a number of studies, but a detailed profile of disease-phenotype specific inflammation has yet to emerge. The heterogeneity of the disease has hindered data interpretation while extrapolation of the results of relatively non-invasive studies to the actual pathology found in the distal lung is difficult. Moreover, prominent studies have had frequently conflicting results. Further investigations are needed to marry the different clinical phenotypes of COPD to their respective inflammatory profiles in the airways and thus improve our understanding of the pathogenesis of the disease as a whole.

Chronic obstructive pulmonary disease: histopathology, inflammation and potential therapies

Chronic obstructive pulmonary disease (COPD) is a major worldwide health burden with increasing morbidity, mortality and health care cost. It is a slowly progressive chronic inflammatory condition that affects the conducting airways (both large and small) and lung parenchyma. In COPD, inflammation is evident early on even in mild disease and increases with disease severity. Recent advances in our knowledge demonstrate, by comparison with asthma, the distinctive, "abnormal" or exaggerated inflammatory processes involved in the pathogenesis of COPD and thus identify novel therapeutic targets that could potentially impact on disease progression. The present review will focus on what is known of the abnormal inflammatory response of COPD in different regions of the conducting airways and lung. Novel, potentially promising approaches to therapy are presented.

COPD: a dust-induced disease?

Various reports have demonstrated the importance of small airway inflammation in the development of airflow limitation and progression of COPD. This hypothesis proposes that the pathogenesis of COPD mirrors a chronic inhalational dust-induced disease. The putative inorganic dust in cigarette smoke is aluminum silicate or kaolinite, a common component of clay soils. Kaolinite has been recovered in the alveolar macrophages of smokers and has been reported as a constituent of tobacco products. The origin of kaolinite in tobacco products remains unknown, and possible potential sources are proposed. On inhalation, kaolinite deposition in the distal lung may promote macrophage accumulation within the terminal airways leading to a respiratory bronchiolitis. In the susceptible smoker, important genetic, environmental, immunologic, and mechanical factors interact and modulate this small airway inflammation, ultimately leading to the pathologic lesion of emphysema. Further studies into the effects of kaolinite on macrophage function and the subsequent development of respiratory bronchiolitis could lead to prevention of COPD at its precursor lesion.

Matrix metalloproteinase-9 promoter polymorphism associated with upper lung dominant emphysema

RATIONALE

Matrix metalloproteinase 9 (MMP-9) has proteolytic activity against connective tissue proteins and appears to play an important role in the development of chronic obstructive pulmonary disease (COPD). The functional polymorphism of MMP-9 (C-1562T) is considered as one of the candidate genes in the susceptibility to COPD.

OBJECTIVES

To determine if MMP-9 (C-1562T) is related to the development of COPD in the Japanese population and whether it is associated with development of pulmonary emphysema assessed by high-resolution computed tomographic (HRCT) parameters.

METHODS

MMP-9 (C-1562T) genotypes of 84 patients with COPD and 85 healthy smokers (control subjects) were determined by the restriction fragment length polymorphism method. We investigated the relationship between the genotypes using automatically analyzed HRCT parameters, such as percentage of low attenuation area (LAA%) and average computed tomography (CT) value density (Hounsfield units; mean CTv) in upper, middle, and lower lung fields in all patients with COPD.

MEASUREMENTS AND MAIN RESULTS

There was no difference in polymorphism of MMP-9 (C-1562T) between patients with COPD and control subjects. In the HRCT study, patients with COPD with a T allele (C/T or T/T) showed larger LAA% (95% confidence interval of difference, 0.5-18.7; p = 0.04), and smaller mean CTv (confidence interval, -34.3 to -1.0; p = 0.04) in the upper lung compared with patients without T alleles (C/C). However, pulmonary function tests showed no difference between the two patient groups. Patients with a T allele showed a decrease in LAA% and an increase in mean CTv from upper to lower lung fields (p = 0.006 and p = 0.002, respectively).

CONCLUSIONS

Polymorphism of MMP-9 (C-1562T) was associated with upper lung dominant emphysema in patients with COPD.

Association between reduced bronchodilatory effect of deep inspiration and loss of alveolar attachments

BACKGROUND

We have previously shown that the bronchodilatory effect of deep inspiration is attenuated in individuals with COPD. This study was designed to investigate whether the impairment in this effect is associated with loss of alveolar attachments.

METHODS

We measured deep inspiration (DI)-induced bronchodilation in 15 individuals with and without COPD (67 +/- 2.2 yrs of age, mean +/- SEM) undergoing lobar resection for peripheral pulmonary nodule. Prior to surgery, we measured TLCO and determined the bronchodilatory effect of deep inspiration after constricting the airways with methacholine. The number of destroyed alveolar attachments, as well as airway wall area and airway smooth muscle area, were determined in tumor-free, peripheral lung tissue.

RESULTS

The bronchodilatory effect of deep inspiration correlated inversely with the % destroyed attachments (r = -0.51, p = 0.05) and directly with the airway smooth muscle area (r = 0.59, p = 0.03), but not with the total wall area (r = 0.39, p = 0.15).

CONCLUSION

We postulate that attenuation of airway stretch due to loss of alveolar attachments contributes to the loss of the bronchodilatory effect of lung inflation in COPD.

Drugs in clinical development for chronic obstructive pulmonary disease

Many drugs may be potentially useful in the treatment of chronic obstructive pulmonary disease (COPD), but relatively few become available for human use due to lack of safety, lack of efficacy, or both. This is an inherent risk in the drug development process, which coupled with the limited understanding of the molecular pathogenesis of COPD, has produced a trend toward improving existing compounds rather than to develop new compounds. This review focuses on improved existing compounds and newly discovered compounds that are in clinical trials, but not yet marketed. The improved existing compounds include: isomers of the long-acting bronchodilators, once-daily beta2-adrenoceptor agonists, anticholinergics and corticosteroids. The pool of novel compounds is in constant fluctuation and comprises anti-inflammatory drugs, antioxidants, leukotriene modifiers and a number of compounds aimed at treating different aspects of COPD such as pulmonary hypertension and hypophosphatemia.

The role of airway smooth muscle in the pathogenesis of airway wall remodeling in chronic obstructive pulmonary disease

Airway wall remodeling processes are present in the small airways of patients with chronic obstructive pulmonary disease, consisting of tissue repair and epithelial metaplasia that contribute to airway wall thickening and airflow obstruction. With increasing disease severity, there is also increased mucous metaplasia and submucosal gland hypertrophy, peribronchial fibrosis, and an increase in airway smooth muscle mass. Apart from its contractile properties, airway smooth muscle produces inflammatory cytokines, proteases, and growth factors, which may contribute to the remodeling process and induce phenotypic changes of the muscle. Airflow limitation responds minimally to beta-agonists and corticosteroid therapy, unlike asthma, perhaps because of alterations in beta-receptor or glucocorticoid receptor numbers, alterations in receptor signaling, or the constrictive limitation imposed by peribronchial fibrosis. Better response is observed with the combination of inhaled long-acting beta-agonists and corticosteroids. This could result from effects at the level of airway smooth muscle. Airway wall remodeling may involve the release of growth factors from inflammatory or resident cells. The influence of smoking cessation or of current therapies on airway wall remodeling is unknown. Specific therapies for airway wall remodeling may be necessary, together with noninvasive methods of imaging small airway wall remodeling to assess responses.

Mechanisms of chronic airway obstruction in smokers

Studies over the past few decades have showed a clear association between cigarette smoking and the development of chronic airway obstruction. Yet, only a minority of smokers is affected so that in many, even heavy, smokers, pulmonary function remains within normal limits. While carcinogens have been well characterized, there is only limited information about the constituents of cigarette smoke responsible for inducing chronic airway obstruction. In addition, the associated risks factors for airway obstruction in smokers have not been totally identified. The present paper is a review of the recently accumulated facts concerning the intimate action of cigarette smoke at the level of large and small airways and lung parenchyma. The role of classical inflammatory cells such as neutrophils and alveolar macrophages is reviewed, but emphasis is put on recent evidence indicating the involvement of CD8 + T-lymphocytes and possibly eosinophils in the genesis of the structural changes leading to airways obstruction. The mechanisms by which airway inflammation and remodelling cause airway narrowing and airflow limitation are discussed, along with the associated loss of lung elasticity secondary to destructive emphysema. Other biological, epidemiological, physiopathological, and clinical aspects are analyzed, stressing such fundamental aspects as the defence mechanisms, the morpho-functional correlations, the identification of susceptible smokers, and the early detection of airway obstruction, both in specialized laboratories and in primary care.

Small airway morphology and lung function in the transition from normality to chronic airway obstruction

This study investigated the relationships between pathological changes in small airways (<6 mm perimeter) and lung function in 22 nonasthmatic subjects (20 smokers) undergoing lung resection for peripheral lesions. Preoperative pulmonary function tests revealed airway obstruction [ratio of forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC) < 70%] in 12 subjects and normal lung function in 10. When all subjects were considered together, total airway wall thickness was significantly correlated with FEV1/FVC (r2 = 0.25), reactivity to methacholine (r2 = 0.26), and slope of linear regression of FVC against FEV1 values recorded during the methacholine challenge (r2 = 0.56). Loss of peribronchiolar alveolar attachments was significantly associated (r2 = 0.25) with a bronchoconstrictor effect of deep inhalation, as assessed from a maximal-to-partial expiratory flow ratio <1, but not with airway responses to methacholine. No significant correlation was found between airway smooth muscle thickness and lung function measurements. In conclusion, this study suggests that thickening of the airway wall is a major mechanism for airway closure, whereas loss of airway-to-lung interdependence may contribute to the bronchoconstrictor effect of deep inhalation in the transition from normal lung function to airway obstruction in nonasthmatic smokers.

Bronchial hyperresponsiveness in patients with squamous cell lung cancer

OBJECTIVE

The aim of this study was to examine the relationship between bronchial hyperresponsiveness, both in vivo and in vitro, and the type of lung cancer (squamous cell or adenocarcinoma).

METHODOLOGY

We measured airway responsiveness by methacholine inhalation test in 33 patients with squamous cell lung cancer and 44 patients with lung adenocarcinoma. In addition, airway smooth muscle reactivity to acetylcholine was measured in vitro in specimens from some patients.

RESULTS

Seventeen of 33 patients with squamous cell cancer and three of 44 patients with adenocarcinoma showed bronchial hyperresponsiveness (BHR). Multiple regression analysis as used to assess the log of the minimum cumulative dose to decrease respiratory conductance vs six variables: cancer phenotype, FEV1 (% predicted), FEV1/FVC (%), smoking pack years, gender and the location of tumour. The phenotype (squamous cell cancer) was the only factor associated with BHR. However, there was no significant difference in airway smooth muscle reactivity to acetylcholine in vitro in bronchial muscle samples from squamous cell cancer patients (n = 6) and adenocarcinoma patients (n = 6).

CONCLUSION

The present findings suggest that bronchial hyperresponsiveness in patients with squamous cell lung cancer is not determined solely by bronchial smooth muscle hyperreactivity.

Effects of fluticasone propionate in COPD patients with bronchial hyperresponsiveness

BACKGROUND

Treatment of chronic obstructive pulmonary disease (COPD) with inhaled corticosteroids does not appear to be as effective as similar treatment of asthma. It seems that only certain subgroups of patients with COPD benefit from steroid treatment. A study was undertaken to examine whether inhaled fluticasone propionate (FP) had an effect on lung function and on indices of inflammation in a subgroup of COPD patients with bronchial hyperresponsiveness (BHR).

METHODS

Twenty three patients with COPD were studied. Patients had to be persistent current smokers between 40 and 70 years of age. Non-specific BHR was defined as a PC(20) for histamine of <or=8 mg/ml. Patients received either 2 x 500 microg FP or placebo for 6 months. Expiratory volumes were measured at monthly visits, BHR was determined at the start of the study and after 3 and 6 months, and bronchial biopsy specimens were taken at the start and after 6 months of treatment. Biopsy specimens from asymptomatic smokers served as controls.

RESULTS

In contrast to asthma, indices of BHR were not significantly influenced by treatment with FP. Forced expiratory volume in 1 second (FEV(1)) showed a steep decline in the placebo group but remained stable in patients treated with FP. FEV(1)/FVC, and maximal expiratory flows at 50% and 25% FVC (MEF(50), MEF(25)) were significantly increased in the FP treated patients compared with the placebo group. Biopsy specimens were analysed for the presence of CD3+, CD4+, CD8+, MBP+, CD15+, CD68+, CD1a, and tryptase cells. FP treatment resulted in marginal reductions in these indices of inflammation.

CONCLUSION

In patients with COPD and BHR, FP has a positive effect on indices of lung function compared with placebo. Bronchial inflammation analysed in bronchial biopsy specimens is only marginally reduced.

Lymphocyte population and apoptosis in the lungs of smokers and their relation to emphysema

Previously, it had been shown that T-lymphocytes are the predominant inflammatory cells found in the alveolar wall of smokers and their numbers correlated with the extent of emphysema. However, the phenotype of these cells was not defined. The aim of this study was to describe the different T-cell phenotypes and investigate the possible presence of apoptosis in the lung parenchyma of smokers. Samples from lungs were obtained at surgery from 15 patients who smoked and six who had never smoked. Samples were frozen and prepared for histological and immunocytochemical examination. Slides were stained for CD3+, CD4+, CD8+, gammadelta T-cells, CD56 natural killers ((NK) cells), and elastase (neutrophils). Anti-CD95 monoclonal antibodies and in situ end-labelling techniques were used to detect Fas expression and apoptosis. Positive staining cells were expressed as cells-mm alveolar wall-, percentage of total cells, and Fas/APO and apoptosis index. Emphysema was identified macroscopically, microscopically and reported as present or absent. All subjects had pulmonary function tests before surgery. Neutrophils were the predominant cell in the lung parenchyma of nonsmokers and smokers without emphysema. In smokers with emphysema, the CD3+ and CD8+ were the predominant cells (p<0.05) in the alveolar wall. gammadelta cells were increased in all smokers and no increased numbers of NK cells was found. The T-cell numbers x mm alveolar wall(-1) showed a bilinear relationship with the amount smoked increasing at an inflection point of 30 packs yr(-1) (R2= 0.345; p < 0.01). Apoptosis in smokers showed a bilinear relationship with the amount smoked increasing sharply in smokers with emphysema (R2=0.3613; p < 0.009). It is concluded that the pathogenesis of emphysema might be mediated by T-lymphocytes, mainly CD8+ cytolytic T-cells, and that apoptosis might be one of the mechanisms of lung destruction leading to the development of emphysema. If this is the case, it could be speculated that T-cell inflammation is a response to antigenic stimuli originating in the lung and induced by cigarette smoking.

Airway inflammation and hyperresponsiveness to adenosine 5'-monophosphate in chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is often accompanied by bronchial hyperresponsiveness (BHR). Measurement of BHR may give information about airway inflammation.

OBJECTIVE

To investigate the role of airway inflammation in hyperresponsiveness to adenosine 5'-monophosphate (AMP) in COPD.

METHODS

We investigated inflammatory indices in induced sputum, bronchoalveolar lavage (BAL) fluid and bronchial biopsies in subjects with COPD with and without hyperresponsiveness to AMP. Twelve nonatopic subjects with COPD with hyperresponsiveness to AMP (mean +/- SD, age 63 +/- 8 years, FEV1% predicted 56 +/- 13%), six without BHR (age 60 +/- 6 years, FEV1% predicted 65 +/- 11%) and 11 healthy nonatopic controls without BHR (age 58 +/- 8 years, FEV1% predicted 104 +/- 11%) participated in the study.

RESULTS

Subjects with COPD with BHR had significantly higher numbers of mucosal CD8 + and higher percentages of sputum eosinophils than those without BHR (median, 550 cells/mm2; range, 30-1340 vs 280 cells/mm2; range, 110-450, P = 0.045; and median, 2.7%; range, 0.5-8.5 vs 0.6%; range, 0-0.8 %, P = 0.0036, respectively). No differences were observed in BAL fluid.

CONCLUSION

We conclude that hyperresponsiveness to AMP in COPD is associated with airway inflammation that is characterized by increased numbers of mucosal CD8 + cells and percentages of sputum eosinophils. Hyperresponsiveness to AMP may be used as a marker of airway inflammation in COPD, but its significance in the clinical course remains to be determined.

Influence of lung parenchymal destruction on the different indexes of the methacholine dose-response curve in COPD patients

STUDY OBJECTIVES

The interpretation of nonspecific bronchial provocation dose-response curves in COPD is still a matter of debate. Bronchial hyperresponsiveness (BHR) in patients with COPD could be influenced by the destruction of the parenchyma and the augmented mechanical behavior of the lung. Therefore, we studied the interrelationships between indexes of BHR, on the one hand, and markers of lung parenchymal destruction, on the other.

PATIENTS AND METHODS

COPD patients were selected by clinical symptoms, evidence of chronic, nonreversible airways obstruction, and BHR, which was defined as a provocative dose of a substance (histamine) causing a 20% fall in FEV(1) (PC(20)) of </= 8 mg/mL. BHR was subsequently studied by methacholine dose-response curves to which a sigmoid model was fitted for the estimation of plateau values and reactivity. Model fits of quasi-static lung pressure-volume (PV) curves yielded static lung compliance (Cstat), the exponential factor (KE) and elastic recoil at 90% of total lung capacity (P90TLC). Carbon monoxide (CO) transfer was measured with the standard single-breath method.

RESULTS

Twenty-four patients were included in the study, and reliable PV data could be obtained from 19. The following mean values ( +/- SD) were taken: FEV(1), 65 +/- 12% of predicted; reversibility, 5.6 +/- 3.1% of predicted; the PC(20) for methacholine, 4.3 +/- 5.2 mg/mL; reactivity, 11.0 +/- 5.6% FEV(1)/doubling dose; plateau, 48.8 +/- 17.4% FEV(1); transfer factor, 76.7 +/- 17.9% of predicted; transfer coefficient for carbon monoxide (KCO), 85.9 +/- 22.6% of predicted; Cstat, 4.28 +/- 2.8 kPa; shape factor (KE), 1.9 +/- 1.5 kPa; and P90TLC, 1.1 +/- 0.8 kPa. We confirmed earlier reported relationships between Cstat, on the one hand, and KE (p < 0.0001), P90TLC (p = 0.0012), and KCO percent predicted (p = 0.006), on the other hand. The indexes of the methacholine provocation test were not related to any parameter of lung elasticity and CO transfer.

CONCLUSION

BHR in COPD patients who smoke most probably is determined by airways pathology rather than by the augmented mechanical behavior caused by lung parenchymal destruction.

Chronic obstructive pulmonary disease. Inflammation of small airways and lung parenchyma

Currently available information suggests that cigarette smoke-induced lung inflammation has a pathogenic role in the development of COPD. Neutrophils, eosinophils, alveolar macrophages, and lymphocytes all appear to participate in the inflammatory process. However, the respective importance of these cells and their level of activation are difficult to quantitate because disease phenotyping, and compartmentalization of inflammation and markers of inflammation in the lung, influence the obtained data and bias their interpretation. Bronchoscopic biopsies are typically obtained from larger, cartilaginous airways containing submucosal glands whereas the site of airflow obstruction in COPD is predominantly the membranous bronchiole, devoid of cartilage and submucosal glands. This makes it difficult to establish structure-function relationships. The proportion of neutrophils has been reported to increase in repeated induced sputum and bronchoalveolar lavage samples. This observation suggests neutrophil recruitment into the airway is induced by the tests or sampling of different airway compartments in subsequent tests. There appears to be a good correlation between the proportions of eosinophils in induced sputum and bronchoalveolar lavage fluid on the one hand and in airway tissue on the other. However, this is not the case for other inflammatory cells, especially T lymphocytes, which are more numerous in airway tissue. Despite these inconsistencies, induced sputum, bronchoalveolar lavage, and bronchial biopsies can be used as markers of inflammation in COPD as long as their limitations are recognized. Cosio MG, Guerassimov A. Chronic obstructive pulmonary disease: inflammation of small airways and lung parenchyma.