The role of inflammation and anti-inflammatory medication in asthma

Asthma is a chronic inflammatory disease of the airways involving a wide range of cells and mediators. First-line therapy of persistent asthma involves the use of inhaled corticosteroids to control the underlying inflammation of the airways. Inhaled beta2-agonists are also widely used in asthma therapy and are the most effective bronchodilators currently available. The short-acting beta2-agonists are now used on an as-needed basis for rapid relief of symptoms, In recent years, long-acting inhaled beta2-agonists have had an increasing role in the management of asthma, particularly in patients with moderate to severe asthma. This class of drug has a long duration of action and is recommended as add-on treatment to inhaled corticosteroids in the long-term control of asthma. New therapies have been added to asthma therapy as our understand ng of the pathogenesis of asthma has increased. The use of multiple therapies necessitates a clear understanding of the mode of action of the drugs and any potential interaction or overlap of effect. For many people asthma is associated with complex therapy; thus treatment developments that simplify asthma treatment are an mportant step forward n asthma management.

Future Advances in COPD Therapy

There is a pressing need for more effective drug treatments for COPD. New bronchodilators include a long-acting anticholinergic tiotropium bromide and a dual beta2-dopamine2-receptor agonist. But no treatments prevent the progression of COPD. Mediator antagonists in development include leukotriene B4 antagonists, chemokine receptor antagonists and more potent antioxidants. The inflammation of COPD is resistant to corticosteroids, so new anti-inflammatory drugs need to be developed. These include phosphodiesterase-4 inhibitors, nuclear factor-kappaB inhibitors and p38 MAP kinase inhibitors. Small molecule protease inhibitors, including neutrophil elastase inhibitors and selective matrix metalloproteinase inhibitors are also in development. Future drug targets may be identified by gene array and proteomics.

Distribution and function of the peptide transporter PEPT2 in normal and cystic fibrosis human lung

BACKGROUND

Aerosol administration of peptide based drugs has an important role in the treatment of various pulmonary and systemic diseases. The characterisation of pulmonary peptide transport pathways can lead to new strategies in aerosol drug treatment.

METHODS

Immunohistochemistry and ex vivo uptake studies were established to assess the distribution and activity of the beta-lactam transporting high affinity proton coupled peptide transporter PEPT2 in normal and cystic fibrosis human airway tissue.

RESULTS

PEPT2 immunoreactivity in normal human airways was localised to cells of the tracheal and bronchial epithelium and the endothelium of small vessels. In peripheral lung immunoreactivity was restricted to type II pneumocytes. In sections of cystic fibrosis lung a similar pattern of distribution was obtained with signals localised to endothelial cells, airway epithelium, and type II pneumocytes. Functional ex vivo uptake studies with fresh lung specimens led to an uptake of the fluorophore conjugated dipeptide derivative D-Ala-L-Lys-AMCA into bronchial epithelial cells and type II pneumocytes. This uptake was competitively inhibited by dipeptides and cephalosporins but not ACE inhibitors, indicating a substrate specificity as described for PEPT2.

CONCLUSIONS

These findings provide evidence for the expression and function of the peptide transporter PEPT2 in the normal and cystic fibrosis human respiratory tract and suggest that PEPT2 is likely to play a role in the transport of pulmonary peptides and peptidomimetics.

Scientific rationale for inhaled combination therapy with long-acting beta2-agonists and corticosteroids

The addition of an inhaled long-acting beta2-agonist (LABA) to an inhaled corticosteroid (ICS) gives optimal control of asthma in most patients and two fixed combination inhalers (salmeterol/fluticasone and formoterol/budesonide) are increasingly used as a convenient controller in patients with persistent asthma. There is a strong scientific rationale for the combination of these two drug classes. ICS suppress the chronic inflammation of asthma and reduce airway hyperresponsiveness and this is achieved at low doses in most patients. LABA act on different aspects of the pathophysiology of asthma. In addition to their bronchodilator action, LABA also inhibit mast cell mediator release, plasma exudation and may reduce sensory nerve activation. Thus these two classes of drug address complementary aspects of the pathophysiology of asthma that neither drug class is able to achieve alone. There are several positive interactions between LABA and ICS. Corticosteroids increase the expression of beta2-receptors by increasing gene transcription. Experimentally this protects against the loss of beta2-receptors in response to long-term exposure to beta2-agonists. While this is unlikely to be important in bronchodilator responses to beta2-agonists, in view of the large beta-receptor reserve, it is probably important in preventing loss of beta-agonist effects on the nonbronchodilator actions of LABA discussed earlier. beta2-Agonists may potentiate the molecular mechanism of corticosteroid actions, with increased nuclear localization of glucocorticoid receptors and additive or sometimes synergistic suppression of inflammatory mediator release. Thus LABA and ICS may optimize each others beneficial actions in the airways, but the low systemic effects of these drugs do not result in any increase in adverse effects. Long-acting beta2-agonists corticosteroid inhaler therapy is therefore a logical advance and results in effective control of asthma in the majority of patients without significant adverse effects. This simplified approach to long-term asthma therapy has a strong scientific rationale.

TGFbeta1 allele association with asthma severity

Transforming growth factor beta1 (TGFbeta1) is a multifunctional cytokine involved in pro- and anti-inflammatory pathways and is expressed in several cell types. Subepithelial fibrosis is one of the principle features of airway remodelling in asthma and is increased in severe patients. TGFbeta1 is implicated in fibrosis, including the deposition of extracellular matrix proteins. TGFbeta1 mRNA levels in eosinophils are increased in severe asthmatics relative to mild asthmatics. Therefore, TGFbeta1 is a promising candidate gene for contributing to asthma severity. Four polymorphisms located in the promoter region and signal peptide (C-509T, 72insC, T869C and G915C) were genotyped in groups of severe asthmatic, mild asthmatic or control individuals defined by steroid usage and pulmonary function. Significant differences ( P=0.016) were found between the groups for the genotype frequencies at C-509T, attributable mainly to a greater relative frequency of homozygosity for the -509T allele in the severe group compared to the mild and control groups. Individuals homozygous for -509T were also homozygous at the other variant sites for the 72C, 869C and 915G alleles (haplotype 1). The T allele creates a putative YY1 transcription factor binding site, but binding between YY1 and the DNA sequence of the T allele was not detected in vitro. In this study, we show that the -509T variant on haplotype 1 is the most informative marker of the TGFbeta1 contribution to asthma severity.

Exhaled carbon monoxide in patients with lower respiratory tract infection

The concentration of carbon monoxide (CO) in exhaled air is increased in patients with asthma, bronchiectasis and upper respiratory tract viral infections. However there is no information about the level of CO in patients with lower respiratory tract infection. We studied a group of 35 patients (22 males) aged 45 +/- 3 (SEM) years with cough productive of purulent phlegm and pyrexia in a general practice setting. All were non-smokers or ex-smokers and none had a previous history of respiratory problems or diabetes. We measured CO level in exhaled air before and after a course of antibiotics. Therapy was deemed successful when patient no longer complained of cough productive of purulent phlegm. Twenty-eight of 35 patients had elevated CO level at their initial visit. Twenty-two out of 35 patients reported clinical improvement after antibiotic treatment and this was associated with a fall in exhaled CO level from 5.2 +/- 0.5 ppm to 2.3 +/- 0.3 ppm (P < 0.0001). We suggest that simple CO measurements in exhaled air can detect the inflammatory process within the airways caused by infection and that a repeat measurement can be used to assess the nature of inflammation.

Cytokine modulators as novel therapies for airway disease

Cytokines play a critical role in orchestrating and perpetuating inflammation in asthma and chronic obstructive pulmonary disease (COPD), and several specific cytokine and chemokine inhibitors are now in development for the future therapy of these diseases. Anti-interleukin (IL)-5 is very effective at reducing peripheral blood and airway eosinophil numbers, but does not appear to be effective against symptomatic asthma. Inhibition of IL4 with soluble IL4 receptors has shown promising early results in asthma. Inhibitory cytokines, such as IL-10, interferons and IL-12 are less promising, as systemic delivery causes side-effects. Inhibition of tumour necrosis factor-alpha may be useful in severe asthma and for treating severe COPD with systemic features. Many chemokines are involved in the inflammatory response of asthma and COPD and several low-molecular-weight inhibitors of chemokine receptors are in development. CCR3 antagonists (which block eosinophil chemotaxis) and CXCR2 antagonists (which block neutrophil and monocyte chemotaxis) are in clinical development for the treatment of asthma and COPD respectively. Because so many cytokines are involved in asthma, drugs that inhibit the synthesis of multiple cytokines may prove to be more useful; several such classes of drug are now in clinical development and any risk of side-effects with these nonspecific inhibitors may be reduced by the use of inhalational route of delivery.

Cytokine modulators for allergic diseases

Cytokines play a critical role in orchestrating and perpetuating inflammation in allergic diseases and several specific cytokine inhibitors now in development for the treatment of asthma and other allergic diseases. The effects of inhibiting the T helper 2 cytokines interleukin-5, interleukin-13 and interleukin-9 are discussed, together with inhibition of tumor necrosis factor-alpha. Inhibitory cytokines, such as interleukin-10, interferons and interleukin-12, are also being considered in the treatment of allergic diseases.

Evidence for systemic rather than pulmonary effects of interleukin-5 administration in asthma

BACKGROUND

Interleukin 5 (IL-5) has an important role in mobilisation of eosinophils from the bone marrow and in their subsequent terminal differentiation. A study was undertaken to determine whether inhaled and intravenous IL-5 could induce pulmonary eosinophilia and bronchial hyperresponsiveness (BHR) independently of these effects.

METHODS

Nine mild asthmatics received inhaled (15 microg) or intravenous (2 microg) IL-5 or placebo in random order in a double blind, crossover study. Blood samples were taken before and at 0.5, 1, 2, 3, 4, 5, 24, and 72 hours following IL-5 or placebo, and bronchial responsiveness (PC(20) methacholine) and eosinophil counts in induced sputum were determined.

RESULTS

Serum IL-5 levels were markedly increased 30 minutes after intravenous IL-5 (p=0.002), and sputum IL-5 levels increased 4 and 24 hours after inhaled IL-5 (p<0.05). Serum eotaxin was raised 24 hours after intravenous IL-5 but not after inhaled IL-5 or placebo. Blood eosinophils were markedly reduced 0.5-2 hours after intravenous IL-5 (p<0.05), followed by an increase at 3, 4, 5, and 72 hours (p<0.05). Sputum eosinophils rose significantly in all three groups at 24 hours but there were no differences between the groups. Bronchial responsiveness was not affected by IL-5.

CONCLUSION

The effects of IL-5 appear to be mainly in the circulation, inducing peripheral mobilisation of eosinophils to the circulation without any effect on eosinophil mobilisation in the lungs or on bronchial responsiveness.

Low-dose theophylline does not exert its anti-inflammatory effects in mild asthma through upregulation of interleukin-10 in alveolar macrophages

BACKGROUND

There is accumulating evidence that theophylline has anti-inflammatory or immunomodulatory effects. This may be, in part, mediated via an upregulation in the production of the anti-inflammatory cytokine interleukin (IL)-10. We determined whether low-dose theophylline (LDT) would increase the production of IL-10, and attenuate the production of proinflammatory cytokines by alveolar macrophages.

METHODS

In a double-blind, placebo-controlled, crossover study involving 15 steroid-free patients with mild asthma, fiberoptic bronchoscopy and bronchoalveolar lavage (BAL) were performed at the end of the treatment and placebo periods. Alveolar macrophages were cultured in vitro, and we measured their release of IL-10, GM-CSF, and TNF-alpha. We also measured IL-10 production in whole blood together with the number of monocytes and T cells expressing intracellular IL-10 by flow cytometry.

RESULTS

LDT did not increase the production of IL-10, or attenuate the production of GM-CSF or TNF-alpha by alveolar macrophages. However, after theophylline treatment, there was a significant reduction in mean (SD) (95% CI) BAL eosinophil number from 3.4 (1.7)% (95% CI 2.4-4.4) to 1.7 (1.0)% (95% CI 1.1-2.3) compared with placebo (P<0.05). Similarly, there was no increase in whole-blood IL-10 release or in the number of monocytes and T cells expressing intracellular IL-10 after treatment.

CONCLUSIONS

LDT has an anti-inflammatory effect in asthma; however, this effect is not mediated via the production of IL-10 or the attenuation of GM-CSF or TNF-alpha. The mechanisms of theophylline activity remain to be determined.

Glucocorticoid-mediated transrepression is regulated by histone acetylation and DNA methylation

Glucocorticoids are highly effective in controlling chronic inflammatory diseases by inhibiting the expression of cytokines and chemokines. Glucocorticoids act through binding of their receptor resulting to inhibition of transcription factors such as nuclear factor kappa B (NF-kappa B). This may occur via the transcription integrator protein, CREB binding protein (CBP), which has intrinsic histone acetylase (HAT) activity. Interleukin (IL)-1 beta caused a significant increase in NF-kappa B-mediated granulocyte/macrophage colony stimulating factor (GM-CSF) release, which was inhibited by the glucocorticoid mometasone furoate (MF) (EC(50)=2 x 10(-11) M). This effect was inhibited by CBP over-expression. The role of histone acetylation and DNA methylation in the transcription of GM-CSF was indicated by trichostatin A (TSA), an inhibitor of histone deacetylases, and 5-azacytidine (5-aza), a DNA methylase inhibitor, to increase GM-CSF expression partially blocking glucocorticoid inhibition of IL-1 beta-stimulated GM-CSF release. These data suggest that the mechanism of glucocorticoid action in suppressing interleukin-1 beta-stimulated GM-CSF release in A549 cells may involve modulation of CBP-mediated histone-acetylase activity and DNA methylation.

Low dose inhaled budesonide and formoterol in mild persistent asthma: the OPTIMA randomized trial

The optimal treatment for mild asthma is uncertain. We assessed the effects of adding a long-acting inhaled beta-agonist, formoterol, to low doses of an inhaled corticosteroid, budesonide, for 1 yr in subjects with mild asthma, receiving no or only a small dose of inhaled corticosteroid. The 698 corticosteroid free patients (Group A) were assigned to twice daily treatment with 100 microg budesonide, 100 microg budesonide plus 4.5 microg formoterol, or placebo. The 1,272 corticosteroid-treated patients (Group B) were assigned to twice daily treatment with 100 microg budesonide, 100 microg budesonide plus 4.5 microg formoterol, 200 microg budesonide, or 200 microg budesonide plus 4.5 microg formoterol. The main outcome variables were time to the first severe asthma exacerbation and poorly controlled asthma days. In Group A, budesonide alone reduced the risk for severe exacerbations by 60% and poorly controlled days by 48%; adding formoterol increased lung function with no change in other end points. By contrast, in Group B, adding formoterol reduced the risk for the first severe exacerbation and for poorly controlled days by 43 and 30%, respectively. Thus, in corticosteroid-free patients, low dose inhaled budesonide alone reduced severe exacerbations and improved asthma control, and in patients already receiving inhaled corticosteroid, adding formoterol was more effective than doubling the corticosteroid dose.

Interleukin-5 induces CD34(+) eosinophil progenitor mobilization and eosinophil CCR3 expression in asthma

Asthma is characterized by the accumulation of activated T cells and eosinophils within the airway. Eosinophils derive from CD34(+) bone marrow progenitor cells under the influence of hematopoietic growth factors, subsequently migrating to the airways under the cooperative influence of interleukin (IL)-5 and chemokines, including eotaxin. We compared the relative effects of systemic versus local IL-5 on progenitor-cell mobilization and mature eosinophil phenotype by using flow cytometry, following the administration of intravenous (2 microg) or inhaled (15 microg) IL-5 to nine patients with mild asthma. Intravenous IL-5 induced a rapid reduction in circulating eosinophil counts followed by prolonged blood eosinophilia. Both intravenous (p < 0.002) and inhaled (p < 0.05) IL-5 significantly increased CD34(+)/CD45(+) lymphoblastoid eosinophil progenitors. Intravenous IL-5 increased mature eosinophil CCR3 expression from a baseline mean fluorescence intensity (MFI) of 658 +/- 51.7 to 995 +/- 93.2 at 24 h (p < 0.05), but had no effect on interleukin-5 receptor subunit alpha or CD11b expression. Lymphocyte CCR3 MFI was increased by intravenous IL-5 from 38.5 +/- 13.6 at baseline to 73.6 +/- 14.3 at 24 h (p < 0.05). Systemic IL-5 increased circulating eosinophil progenitors, suggesting a key role for systemic IL-5 in eosinophil mobilization. Further, IL-5 causes terminal maturation of the eosinophil by increasing CCR3 expression, potentially affecting CCR3-dependent chemotaxis by eosinophils and lymphocytes.

Elevated concentrations of exhaled hydrogen peroxide in asthmatic patients

BACKGROUND

Airway inflammation is important in the development and progression of asthma. Activation of inflammatory cells induces a respiratory burst resulting in the production of reactive oxygen species, such as H(2)O(2). The aim of this study was to measure the concentration of H(2)O(2) in exhaled breath condensate and its correlation with airway obstruction, airway hyperresponsiveness, and concentration of eosinophil cationic protein (ECP) in serum in 70 steroid-naive, atopic patients with unstable asthma (20 men; age range, 18 to 62 years) and 17 normal subjects (7 men; age range, 19 to 34 years).

METHODS

Exhaled H(2)O(2) was measured using a colorimetric assay, and the concentration of ECP in serum was measured using radioimmunoassay. Airway hyperresponsiveness was expressed as the provocative concentration of inhaled histamine causing a 20% fall in FEV(1) (PC(20)).

RESULTS

In patients with asthma, the mean H(2)O(2) concentration was significantly elevated compared to values in normal subjects: 0.127 +/- 0.083 mol/L vs 0.024 +/- 0.016 mol/L (p < 0.001). There was a significant correlation among H(2)O(2) concentration, FEV(1), PC(20), and ECP in serum.

CONCLUSION

We conclude that exhaled H(2)O(2) is significantly elevated in asthmatic patients. This is correlated with disease severity and indirect markers of airway inflammation. Measurement of exhaled H(2)O(2) may be useful to assess airway inflammation and oxidative stress in asthmatic patients.

GM-CSF expression in pulmonary epithelial cells is regulated negatively by posttranscriptional mechanisms

Incubation of pulmonary A549 cells with D609, a phosphatidyl-choline specific phospholipase C (PC-PLC)-inhibitor, or the anti-oxidant, pyrrolidine dithiocarbamate (PTDC), markedly increased IL-1beta-induced GM-CSF elaboration. This effect was observed at the mRNA level and could be partially reproduced by the protein synthesis inhibitor, cycloheximide. Following the peak in GM-CSF mRNA, the mRNA half-life (t(1/2)) was 0.5-1 h. This was increased to around 3 h by cycloheximide, whilst following D609 or PDTC treatment there was essentially no degradation. These data suggest the existence of inhibitory pathways that posttranscriptionally regulate GM-CSF expression via new protein synthesis and D609- and PDTC-sensitive steps. These observations may have important clinical implications. First, drugs that target gene induction may also knock out these inhibitory pathways to lessen their effect. Second, defects in such pathways could lead to overexpression of cytokines or growth factors and contribute to the pathogenesis of inflammatory or proliferative diseases.

Expression of GATA family of transcription factors in T-cells, monocytes and bronchial biopsies

GATA-binding proteins are a subfamily of zinc finger transcription factors with six members (GATA-1-6) that interact with the GATA deoxyribonucleic acid (DNA) sequence. This sequence is found in the regulatory regions of many genes including those encoding T-helper 2 (Th2)-like cytokines, receptors, adhesion molecules and enzymes, which may be important in the pathogenesis of bronchial asthma. The expression of GATA-3, 4 and -6 was investigated in peripheral blood T-lymphocytes and monocytes and bronchial biopsies from 11 normal subjects and 10 steroid-naive asthmatic patients. Using Western blot analysis, T-cells from asthmatic subjects expressed 5 times the level of GATA-3 compared to that in normals. Confocal microscopy indicated that GATA-3 expression was both nuclear and cytoplasmic. GATA DNA binding complex containing GATA-3 was elevated in Th2 cells as determined by electrophorectic mobility shift assay. In contrast, monocytes from normal and asthmatic subjects expressed GATA-4 and -6 in equal amounts, but no GATA-3 was found. Using immunohistochemistry in bronchial biopsies, epithelial cells expressed high levels of GATA-3, GATA-4 and GATA-6 proteins. Comparison of Western blots of bronchial biopsies showed no significant differences between normal and asthmatic subjects. In conclusion, the increased expression of GATA-3 in asthmatic T-cells may underlie augmented T-helper 2-like cytokines in this disease. However, the unaltered GATA-3 expression in epithelial cells suggests a distinct role for GATA-3 in these cells unrelated to T-helper 2-like cytokine release. Finally, no evidence was found for an increased expression of GATA-4 and GATA-6 in asthma.

Adenosine 3',5'-cyclic monophosphate (cAMP)-dependent inhibition of IL-5 from human T lymphocytes is not mediated by the cAMP-dependent protein kinase A

IL-5 is implicated in the pathogenesis of asthma and is predominantly released from T lymphocytes of the Th2 phenotype. In anti-CD3 plus anti-CD28-stimulated PBMC, albuterol, isoproterenol, rolipram, PGE2, forskolin, cholera toxin, and the cAMP analog, 8-bromoadenosine cAMP (8-Br-cAMP) all inhibited the release of IL-5 and lymphocyte proliferation. Although all of the above compounds share the ability to increase intracellular cAMP levels and activate protein kinase (PK) A, the PKA inhibitor H-89 failed to ablate the inhibition of IL-5 production mediated by 8-Br-cAMP, rolipram, forskolin, or PGE2. Similarly, H-89 had no effect on the cAMP-mediated inhibition of lymphocyte proliferation. Significantly, these observations occurred at a concentration of H-89 (3 microM) that inhibited both PKA activity and CREB phosphorylation in intact cells. Additional studies showed that the PKA inhibitors H-8, 8-(4-chlorophenylthio) adenosine-3',5'-cyclic monophosphorothioate Rp isomer, and a myristolated PKA inhibitor peptide also failed to block the 8-Br-cAMP-mediated inhibition of IL-5 release from PBMC. Likewise, a role for PKG was considered unlikely because both activators and inhibitors of this enzyme had no effect on IL-5 release. Western blotting identified Rap1, a downstream target of the cAMP-binding proteins, exchange protein directly activated by cAMP/cAMP-guanine nucleotide exchange factors 1 and 2, in PBMC. However, Rap1 activation assays revealed that this pathway is also unlikely to be involved in the cAMP-mediated inhibition of IL-5. Taken together, these results indicate that cAMP-elevating agents inhibit IL-5 release from PBMC by a novel cAMP-dependent mechanism that does not involve the activation of PKA.

p65-activated histone acetyltransferase activity is repressed by glucocorticoids: mifepristone fails to recruit HDAC2 to the p65-HAT complex

Glucocorticoids acting through their specific receptor can either enhance or repress gene transcription. Dexamethasone represses interleukin-1beta-stimulated histone acetylation and granulocyte-macrophage colony-stimulating factor expression through a combination of direct inhibition of p65-associated histone acetyltransferase (HAT) activity and by recruiting histone deacetylase 2 (HDAC2) to the p65-HAT complex. Here we show that mifepristone, a glucocorticoid receptor partial agonist, has no ability to induce gene expression but represses interleukin-1beta-stimulated histone acetylation and granulocyte-macrophage colony-stimulating factor release by 50% maximally. Mifepristone was able to inhibit p65-associated HAT activity to the same extent as dexamethasone but failed to inhibit the natural promoter to an equal extent due to an inability to recruit HDAC2 to the p65-associated HAT complex. These data suggest that the maximal repressive actions of glucocorticoids require recruitment of HDAC2 to a p65-HAT complex. These data also suggest that pharmacological manipulation of specific histone acetylation status is a potentially useful approach for the treatment of inflammatory diseases.

Exhaled carbon monoxide and nitric oxide in COPD

STUDY OBJECTIVES

To investigate whether exhaled carbon monoxide (CO) and nitric oxide (NO) could be used as noninvasive in vivo biomarkers of oxidative stress in the lungs of patients with COPD.

DESIGN

Single-center cross-sectional study.

PATIENTS

Ten healthy nonsmokers, 12 smokers, 15 stable ex-smokers with COPD, and 15 stable current smokers with COPD.

INTERVENTIONS

Subjects attended the outpatient clinic on one occasion for pulmonary function tests and exhaled CO and NO measurements.

MEASUREMENTS AND RESULTS

Mean (+/- SEM) CO levels in ex-smokers with COPD were higher (7.4 +/- 1.9 ppm; p < 0.05) than in nonsmoking control subjects (3.0 +/- 0.3 ppm) but were lower than in current smokers with COPD (20.0 +/- 2.6 ppm; p < 0.001). There was no correlation between exhaled CO and NO. There was no correlation between CO and lung function tests in any group of patients. Exhaled NO was higher in ex-smokers with COPD (12.0 +/- 1.0 parts per billion [ppb]; p < 0.001) than in healthy nonsmokers (6.5 +/- 0.6 ppb) and in current smokers with COPD (7.6 +/- 1.1 ppb; p < 0.01) compared to healthy smokers (3.3 +/- 0.4 ppb). Ex-smokers with COPD had higher exhaled NO levels than did current smokers with COPD (p < 0.001) There was a negative correlation between exhaled NO and FEV(1) in both ex-smokers with COPD (r = -0.60; p < 0.02) and current smokers with COPD (r = -0.59; p < 0.02).

CONCLUSION

The measurement of exhaled CO and NO may represent a new method for the noninvasive monitoring of airway inflammation and oxidant stress in COPD ex-smokers. Exhaled CO and NO are strongly affected by cigarette smoking, which limits their usefulness as biomarkers in current smokers.

Cytokine-directed therapies for asthma

Increasing knowledge of the pathophysiologic roles of various cytokines in atopic diseases has provided the basis for the development of novel therapies. Strategic approaches for cytokine inhibition include the blocking of transcription factors that lead to their expression, blockade after their release, cytokine receptor antagonism, and the inhibition of signaling pathways that are activated after cytokine-receptor binding. The proinflammatory cytokines IL-5, IL-4, IL-13, and TNF-alpha are among the therapeutic targets. Results with a humanized anti-IL-5 have been disappointing. Although successful in markedly reducing circulating eosinophils and in preventing eosinophil accumulation in airways, the humanized anti-IL-5 was unable to affect early or late responses to allergen or to reduce airway reactivity to methacholine challenge in patients with asthma. On the other hand, a soluble IL-4 receptor antagonist has shown clinical benefits for patients with moderate asthma who require daily inhaled corticosteroids. Agents that target IL-13 and TNF-alpha remain to be evaluated in asthmatic inflammation. The use of cytokines with anti-inflammatory effects may also have therapeutic value. The evaluation of such agents in human beings, including IL-10, IL-12, and IFN-gamma, is at a preliminary stage, but so far results have not been encouraging.