The New England Journal of Medicine -- July 27, 2000 -- Vol. 343, No. 4

1. The New England Journal of Medicine -- July 27, 2000 -- Vol. 343, No. 4 Chronic Obstructive Pulmonary Disease Peter J. Barnes

2. COPD • chronic obstructive bronchitis, with obstruction of small airways • emphysema, with enlargement of air spaces and destruction of lung parenchyma, loss of lung elasticity, and closure of small airways.

3. COPD Chronic obstructive bronchitis, with obstruction of small airways. Emphysema, with enlargement of air spaces and destruction of lung parenchyma, loss of lung elasticity, and closure of small airways Chronic bronchitis By contrast, is defined by the presence of a productive cough of more than three months' duration for more than two successive years.

4. Most patients with COPD have all three pathologic conditions, but the relative extent of emphysema and obstructive bronchitis within individual patients can vary • chronic obstructive bronchitis • emphysema, and • mucus plugging

5. Epidemiology • 14 million people in the United States have COPD. • 14 percent of white male smokers, as compared with approximately 3 percent of white male nonsmokers • COPD is now the fourth leading cause of death in the United States, and it is the only common cause of death that is increasing in incidence. • The World Health Organization predicts that by 2020 COPD will rise from its current ranking as the 12th most prevalent disease worldwide to the 5th and from the 6th most common cause of death to the 3rd.

6. In patients with (alpha)1-antitrypsin deficiency, as shown by a proteinase inhibitor phenotype (PiZZ) with (alpha)1-antitrypsin levels below 10 percent of normal values, early emphysema develops that is exacerbated by smoking, indicating a clear genetic predisposition to COPD However, less than 1 percent of patients with COPD have (alpha)1-antitrypsin deficiency, and many other genetic variants of (alpha)1-antitrypsin that are associated with lower-than-normal serum levels of this proteinase inhibitor have not been clearly associated with an increased risk of COPD Molecular Genetics

7. COPD is 10 times the normal level in a Taiwanese population with a polymorphism in the promoter region of the gene for tumor necrosis factor (alpha) (TNF-(alpha)) that is associated with increased TNF-(alpha) production. However, members of a British population with the same polymorphism do not have an increased risk of COPD. Molecular Genetics

8. Molecular Genetics • A polymorphic variant of microsomal epoxide hydrolase, an enzyme involved in the metabolism of epoxides that may be generated in tobacco smoke, has been associated with a quintupling of the risk of COPD. • Matched cigarette smokers with and without COPD are being compared by techniques such as DNA microarray (gene chips) to detect single-nucleotide polymorphisms, two-dimensional gel electrophoresis to detect novel proteins (proteomics), and differential display to assess which known and novel genes are expressed.

9. Risk Factors • In industrialized countries, cigarette smoking accounts for most cases of COPD, • In developing countries other environmental pollutants, such as particulates associated with cooking in confined spaces, are important causes. • Air pollution (particularly with sulfur dioxide and particulates), exposure to certain occupational chemicals (such as cadmium), and passive smoking may all be risk factors. • Low birth weight is also a risk factor for COPD, probably because poor nutrition in fetal life results in small lungs, so that the normal decline in lung function with age starts from a lower peak value

10. Not important Risk Factors • Airway hyperresponsiveness and allergy • Atopy, serum IgE concentrations, and blood eosinophilia

11. Lung Health Study showed that increased airway responsiveness to inhaled methacholine was a predictor of an accelerated decline in lung function over a period of five years. However, this is not necessarily the same type of abnormal airway responsiveness that is seen in asthma. age starts from a lower peak value

12. Inflammation now apparent that there is a chronic inflammatory process in COPD, but it differs markedly from that seen in asthma, with different inflammatory cells, mediators, inflammatory effects, and responses to treatment

13. Most inflammation in COPD occurs in the peripheral airways (bronchioles) and lung parenchyma. The bronchioles are obstructed by fibrosis and infiltration with macrophages and T lymphocytes. Destruction of lung parenchyma and an increased number of macrophages and T lymphocytes, which are predominantly CD8+ (cytotoxic) T cells. In contrast to the situation with asthma, eosinophils are not prominent except during exacerbations or in patients with concomitant asthma

14. Inflammatory Cells and Mediators • Cigarette smoke and other irritants activate macrophages and airway epithelial cells in the respiratory tract, which release neutrophil chemotactic factors, including interleukin-8 and leukotriene B4. Neutrophils and macrophages then release proteases that break down connective tissue in the lung parenchyma, resulting in emphysema, and also stimulate mucus hypersecretion. Proteases are normally counteracted by protease inhibitors, including (alpha)1-antitrypsin, secretory leukoprotease inhibitor, and tissue inhibitors of matrix metalloproteinases. Cytotoxic T cells (CD8+ lymphocytes) may also be involved in the inflammatory cascade. MCP-1 denotes monocyte chemotactic protein 1, which is released by and affects macrophages

15. The concentration of leukotriene B4, which is chemotactic for neutrophils, is increased in the sputum of patients with COPD. • Concentrations of the cytokines TNF-(alpha) and the neutrophil-chemotactic chemokine interleukin-8 are also increased in the sputum of patients with COPD. • Macrophages appear to play a critical part, since these cells are 5 to 10 times more numerous, are activated, are localized to sites of damage, and also have the capacity to produce all of the pathologic changes of COPD. • Macrophages may be activated by cigarette smoke and other irritants to release neutrophil-chemotactic factors, such as leukotriene B4 and interleukin-8. Neutrophils and macrophages release multiple proteinases that break down connective tissue in the lung parenchyma, resulting in emphysema, and stimulate mucus secretion • The role of cytotoxic T cells is not yet clear, but they may be involved in the apoptosis and destruction of alveolar-wall epithelial cells through the release of perforins and TNF-(alpha

16. neutrophil elastase and proteinase 3, which are neutrophil-derived serine proteases, and on cathepsins, all of which can produce emphysema in laboratory animals. serine proteases are potent stimulants of mucus secretion and may have an important role in the mucus hypersecretion seen in chronic bronchitis. Neutrophil elastase is inhibited by (alpha)1-antitrypsin in the lung parenchyma and almost certainly accounts for the emphysema in (alpha)1-antitrypsin deficiency, but its role in smoking-related emphysema is less certain. The concentrations of neutrophil elastase in complex with (alpha)1-antitrypsin are elevated in patients with emphysema Protease-Antiprotease Imbalance

17. In patients with emphysema, there is an increase in concentrations in bronchoalveolar-lavage fluid and expression by macrophages of matrix metalloproteinase-1 (collagenase) and matrix metalloproteinase-9 (gelatinase B). Although there are doubts about the importance of matrix metalloproteinase-12 in human macrophages, this result demonstrates the capacity of matrix metalloproteinases to induce emphysema. Matrix metalloproteinases may generate chemotactic peptides that promote recruitment of macrophages to the parenchyma and airways. Metalloproteinases

18. Normally, all of these proteolytic enzymes are counteracted by antiproteases • Inhibitors of serine proteases • (alpha)1-antitrypsin in lung parenchyma • airway-epithelium-derived secretory leukoprotease inhibitor in the airways • Three tissue inhibitors of matrix metalloproteinases (called TIMP-1, TIMP-2, and TIMP-3) counteract matrix metalloproteinases.

19. Cigarette smoking may induce inflammation and increased release of proteases that are counteracted by antiproteases in amounts sufficient to prevent parenchymal injury, but in smokers in whom COPD develops, the production of antiproteases may be inadequate to neutralize the effects of multiple proteases, perhaps because of genetic polymorphisms that impair the function or production of these proteins

20. In chronic obstructive pulmonary disease the balance appears to be tipped in favor of increased proteolysis, because of either an increase in proteases, including neutrophil elastase, cathepsins, and matrix metalloproteinases, or a deficiency of antiproteases, which may include (alpha)1-antitrypsin, elafin, secretory leukoprotease inhibitor, and tissue inhibitors of matrix metalloproteinases

21. Oxidative Stress • increase in the concentration of hydrogen peroxide in the exhaled breath condensates of patients with COPD, particularly during exacerbations • increased breath and urinary concentrations of 8-isoprostane, a marker of oxidative stress. • oxidative stress may exacerbate COPD through several mechanisms: • activation of the transcription factor nuclear factor-(kappa)B (NF-(kappa)B), which switches on the genes for TNF-(alpha), interleukin-8, and other inflammatory proteins, and • oxidative damage of antiproteases, such as (alpha)1-antitrypsin and secretory leukoprotease inhibitor, thus enhancing inflammation and proteolytic injury

22. Oxidative Stress in Chronic Obstructive Pulmonary Disease • decreased antiprotease defenses • activation of nuclear factor-(kappa)B, resulting in increased secretion of the cytokines interleukin-8 and tumor necrosis factor (alpha) • increased production of isoprostanes • direct effects on airway functions • O2- superoxide anion, H2O2- hydrogen peroxide, OH• hydroxyl radical, and ONOO- peroxynitrate

23. Introduction

24. There is evidence of systemic oxidative stress in COPD, with increased release of reactive oxygen species and expression of adhesion molecules in circulating neutrophils Circulating concentrations of interleukin-6 and of acute-phase proteins, such as C-reactive protein, are also increased even in the stable state, although they are further increased during exacerbations. Weight loss in COPD, as in other chronic inflammatory diseases, has been associated with increased circulating levels of TNF-(alpha) and soluble TNF receptors and with increased release of TNF-(alpha) from circulating cells Systemic Effects

25. Weight loss in COPD • Increased circulating levels of leptin, which may contribute to weight loss in these patients. • Increased metabolism and is largely explained by a loss of skeletal muscle and wasting of limb muscles. • Skeletal-muscle weakness is a common feature of COPD and exacerbates dyspnea. • The weakness is due to a combination of chronic hypoxia, immobility, and increased metabolic rate. • There is a profound decrease in myosin heavy chain in these muscles.

26. Amplifying Mechanisms • accelerated decline in lung function may be due to amplification of the normal pulmonary response to irritants, either because of increased production of inflammatory proteins and enzymes or because of defective endogenous antiinflammatory or antiprotease mechanisms • latent viral infection-adenovirus sequence E1A • COPD in patients who have stopped smoking many years before their first symptoms develop...

27. It is now evident that many exacerbations in COPD, as in asthma, are due to upper respiratory tract viral infections (such as rhinovirus infection) and to environmental factors, such as air pollution and temperature. There is an increase in neutrophils and in the concentrations of interleukin-6 and interleukin-8 in sputum during an exacerbation, and patients who have frequent exacerbations have higher levels of interleukin-6, even when COPD is stable. Bronchial biopsies show an increase in eosinophils during exacerbations in patients with mild COPD but there is no increase in sputum eosinophils during exacerbations in patients with severe COPD. An increase in markers of oxidative stress and exhaled nitric oxide, presumably reflecting increased airway inflammation, is observed during exacerbations. Acute Exacerbations

28. Advances in Drug Therapy • Antismoking Measures • New Bronchodilators • Antibiotics • Oxygen • Corticosteroids • Noninvasive Ventilation • Pulmonary Rehabilitation • Lung-Volume-Reduction Surgery • Mediator Antagonists • Protease Inhibitors • New Antiinflammatory Drugs

29. Antismoking Measures • Smoking cessation is the only measure that will slow the progression of COPD, as confirmed in the large Lung Health Study. • Nicotine-replacement therapy (by gum, transdermal patch, or inhaler) provides help to patients in quitting smoking. The use of the recently introduced drug bupropion, a noradrenergic antidepressant, has proved to be the most effective strategy to date. A recent controlled trial showed that after a 9-week course of bupropion, abstinence rates were 30 percent at 12 months, as compared with only 15 percent with placebo. The abstinence rate was slightly improved with the addition of a nicotine patch.

30. Bronchodilators are the mainstay of current drug therapy for COPD.

31. New Bronchodilators • Bronchodilators cause only a small (<10 percent) increase in FEV1 in patients with COPD, but these drugs may improve symptoms by reducing hyperinflation and thus dyspnea, and they may improve exercise tolerance, despite the fact that there is little improvement in spirometric measurements

32. New Bronchodilators • Several studies have demonstrated the usefulness of the long-acting inhaled (beta)2-agonists salmeterol and formoterol in COPD. • An additional benefit of long-acting (beta)2-agonists in COPD may be a reduction in infective exacerbations, since these drugs reduce the adhesion of bacteria such as Haemophilus influenzae to airway epithelial cells.

33. New Bronchodilators • COPD appears to be more effectively treated by anticholinergic drugs than by (beta)2-agonists, in sharp contrast to asthma, for which (beta)2-agonists are more effective. • A new anticholinergic drug, tiotropium bromide, which is not yet available for prescription, has a prolonged duration of action and is suitable for once-daily inhalation in COPD.

34. Antibiotics • Acute exacerbations of COPD are commonly assumed to be due to bacterial infection, since they may be associated with increased volume and purulence of the sputum. • Exacerbations may be due to viral infections of the upper respiratory tract or may be noninfective, so that antibiotic treatment is not always warranted.

35. Antibiotics • A meta-analysis of controlled trials of antibiotics in COPD showed a statistically significant but small benefit of antibiotics in terms of clinical outcome and lung function. • Although antibiotics are still widely used for exacerbations of COPD, methods to diagnose bacterial infection reliably in the respiratory tract are needed so that antibiotics are not used inappropriately. There is no evidence that prophylactic antibiotics prevent acute exacerbations

36. There is no evidence that prophylactic antibiotics prevent acute exacerbations

37. Oxygen • Long-term oxygen therapy: • reduced mortality • improvement in quality of life in patients with severe COPD and chronic hypoxemia (partial pressure of arterial oxygen, <55 mm Hg).

38. Oxygen does not increase survival in patients with less severe hypoxemia.The selection of patients is important in prescribing this expensive therapy.

39. In patients with COPD who have nocturnal hypoxemia, nocturnal treatment with oxygen does not appear to increase survival or delay the prescription of continuous oxygen therapy

40. Corticosteroids • Inhaled corticosteroids are now the mainstay of therapy for chronic asthma, • However, the inflammation in COPD is not suppressed by inhaled or oral corticosteroids, even at high doses. • This lack of effect may be due to the fact that corticosteroids prolong the survival of neutrophils and do not suppress neutrophilic inflammation in COPD.

41. Approximately 10 percent of patients with stable COPD have some symptomatic and objective improvement with oral corticosteroids. It is likely that these patients have concomitant asthma, since both diseases are very common. Indeed, airway hyperresponsiveness, a characteristic of asthma, may predict an accelerated decline in FEV1 in patients with COPD.

42. long-term treatment with high doses of inhaled corticosteroids reduced the progression of COPD, even when treatment was started before the disease became symptomatic. • Inhaled corticosteroids may slightly reduce the severity of acute exacerbations, but it is unlikely that their use can be justified in view of the risk of systemic side effects in these susceptible patients and the expense of using high-dose inhaled corticosteroids for several years.

43. By contrast, two recent studies have demonstrated a beneficial effect of systemic corticosteroids in treating acute exacerbations of COPD, with improved clinical outcome and reduced length of hospitalization. • The reasons for this discrepancy between the responses to corticosteroids in acute and chronic COPD may be related to differences in the inflammatory response (such as increased numbers of eosinophils) or airway edema in exacerbations.

44. Noninvasive Ventilation

45. noninvasive positive-pressure ventilation with a simple nasal mask • which eliminates the necessity for endotracheal intubation, • reduces the need for mechanical ventilation in acute exacerbations of COPD in the hospital, • used at home may improve oxygenation and reduce hospital admissions in patients with severe COPD and hypercapnia • The combination of noninvasive positive-pressure ventilation and long-term oxygen therapy may be more effective,

46. Pulmonary Rehabilitation • Pulmonary rehabilitation consisting of a structured program of education, exercise, and physiotherapy has been shown in controlled trials to improve exercise capacity and quality of life among patients with severe COPD and to reduce the amount of health care needed

47. Lung-Volume-Reduction Surgery • The reduction in hyperinflation improves the mechanical efficiency of the inspiratory muscles • Careful selection of patients after a period of pulmonary rehabilitation is essential. • Patients with localized upper-lobe emphysema appear to do best; relatively low lung resistance during inspiration appears to be a good predictor of improved FEV1 after surgery.

48. Functional improvements • increased FEV1, • reduced total lung capacity and functional residual capacity, • improved function of respiratory muscles, • improved exercise capacity, and • improved quality of life.

50. Mediator Antagonists • 5-lipoxygenase inhibitors, which prevent the synthesis of leukotriene B4, and specific leukotriene B4 antagonists, several of which are now being evaluated for the treatment of COPD. • Specific antagonists of CXCR2, one of the receptors on neutrophils that are activated by interleukin-8, have been developed, and humanized antibodies and soluble receptors that block TNF-(alpha) have already been developed for use in other chronic inflammatory diseases.