Normal bronchial blood flow in COPD is unaffected by inhaled corticosteroids and correlates with exhaled nitric oxide

Role of oxidative stress in the pathogenesis of COPD

Chronic inhalation of cigarette smoke is a prominent cause of chronic obstructive pulmonary disease (COPD) and provides an important source of exogenous oxidants. In addition, several inflammatory and structural cells are a source of endogenous oxidants in the lower airways of COPD patients, even in former smokers. This suggests that oxidants play a key role in the pathogenesis of COPD. This oxidative stress is counterbalanced by the protective effects of the various endogenous antioxidant defenses of the lower airways. A large amount of data from animal models and patients with COPD have shown that both the stable phase of the disease, and during exacerbations, have increased oxidative stress in the lower airways compared with age-matched smokers with normal lung function. Thus, counteracting the increased oxidative stress may produce clinical benefits in COPD patients. Smoking cessation is currently the most effective treatment of COPD patients and reduces oxidative stress in the lower airways. In addition, many drugs used to treat COPD have some antioxidant effects, however, it is still unclear if their clinical efficacy is related to pharmacological modulation of the oxidant/antioxidant balance. Several new antioxidant compounds are in development for the treatment of COPD.

Dynamics of exhaled breath temperature after smoking a cigarette and its association with lung function changes predictive of COPD risk in smokers: a cross-sectional study

Exhaled breath temperature (EBT) is a biomarker of inflammation and vascularity of the airways already shown to predict incident COPD. This cross-sectional study was aimed to assess the potential of EBT in identifying "healthy" smokers susceptible to cigarette smoke toxicity of the airways and to the risk of developing COPD by analysing the dynamics of EBT after smoking a cigarette and its associations with their demographics (age, smoking burden) and lung function. The study included 55 current smokers of both sexes, 29-62 years of age, with median smoking exposure of 15 (10-71.8) pack-years. EBT was measured at baseline and 5, 15, 30, 45, and 60 min after smoking a single cigarette. Lung function was measured with spirometry followed by a bronchodilator test. To compare changes in EBT between repeated measurements we used the analysis of variance and the area under the curve (EBTAUC) as a dependent variable. Multivariate regression analysis was used to look for associations with patient characteristics and lung function in particular. The average (±SD) baseline EBT was 33.42±1.50 °C. The highest significant increase to 33.84 (1.25) °C was recorded 5 min after the cigarette was smoked (p=0.003), and it took one hour for it to return to the baseline. EBTAUC showed significant repeatability (ICC=0.85, p<0.001) and was significantly associated with age, body mass index, number of cigarettes smoked a day, baseline EBT, and baseline FEF75 (R2=0.39, p<0.001 for the model). Our results suggest that EBT after smoking a single cigarette could be used as early risk predictor of changes associated with chronic cigarette smoke exposure.

Structure-function relationship in COPD revisited: an in vivo microscopy view

BACKGROUND

Fibred confocal fluorescence microscopy (FCFM) is a novel technology that allows the in vivo assessment and quantification during bronchoscopy of the bronchial wall elastic fibre pattern, alveolar and vessel diameters and thickness of the elastic fibre in the alveolar wall.

AIMS

To relate these structural characteristics with lung function parameters in healthy subjects, smokers with normal spirometry and patients with chronic obstructive pulmonary disease (COPD).

METHODS

We performed FCFM in 20 never smokers, 20 smokers with normal spirometry and 23 patients with COPD who required bronchoscopy for clinical reasons. The bronchial wall elastic fibre pattern was classified as lamellar, loose and mixed pattern, and later confirmed pathologically. Airspace dimensions and extra-alveolar vessel diameters were measured. Lung function measurements and pulmonary CT scans were obtained in all participants.

RESULTS

Patients with COPD were characterised by a significantly higher prevalence of loose fibre bronchial deposition pattern and larger alveolar diameter which correlated inversely with several lung function parameters (forced expiratory volume in 1 s (FEV1) , FEV1/forced vital capacity ratio, maximum expiratory flow, carbon monoxide transfer factor and carbon monoxide transfer coefficient; p<0.05). Increased alveolar macrophages were demonstrated in active smokers with or without COPD.

CONCLUSIONS

This is the first FCFM study to describe in vivo microscopic changes in the airways and alveoli of patients with COPD that are related to lung function impairment. These findings open the possibility of assessing the in vivo effects of therapeutic interventions for COPD in future studies.

Effects of dietary nutrients on volatile breath metabolites

Breath analysis is becoming increasingly established as a means of assessing metabolic, biochemical and physiological function in health and disease. The methods available for these analyses exploit a variety of complex physicochemical principles, but are becoming more easily utilised in the clinical setting. Whilst some of the factors accounting for the biological variation in breath metabolite concentrations have been clarified, there has been relatively little work on the dietary factors that may influence them. In applying breath analysis to the clinical setting, it will be important to consider how these factors may affect the interpretation of endogenous breath composition. Diet may have complex effects on the generation of breath compounds. These effects may either be due to a direct impact on metabolism, or because they alter the gastrointestinal flora. Bacteria are a major source of compounds in breath, and their generation of H₂, hydrogen cyanide, aldehydes and alkanes may be an indicator of the health of their host.

The effect of β-2 adrenoreceptor agonist inhalation on lungs donated after cardiac death in a canine lung transplantation model

BACKGROUND

It is a matter of great importance in a donation after cardiac death to attenuate ischemia-reperfusion injury (IRI) related to the inevitable warm ischemic time.

METHODS

Donor dogs were rendered cardiac-dead and left at room temperature. The dogs were allocated into 2 groups: the β-2 group (n = 5) received an aerosolized β-2 adrenoreceptor agonist (procaterol, 350 μg) and ventilation with 100% oxygen for 60 minutes starting at 240 minutes after cardiac arrest, and the control group (n = 6) received an aerosolized control solvent with the ventilation. Lungs were recovered 300 minutes after cardiac arrest. Recipient dogs underwent left single-lung transplantation to evaluate the functions of the left transplanted lung for 240 minutes after the reperfusion.

RESULTS

Oxygenation and dynamic compliance were significantly higher in the β-2 group than in the control group. The β-2 group revealed significantly higher levels of cyclic adenosine monophosphate and high-energy phosphates in the donor lung after the inhalation than before it. Histologic findings revealed that the β-2 group had less edema and fewer inflammatory cells.

CONCLUSION

Our results suggest that β-2 adrenoreceptor agonist inhalation during the pre-procurement period may ameliorate IRI.

Role of Inhaled Steroids in Vascular Airway Remodelling in Asthma and COPD

In chronic obstructive airway diseases, such as asthma and chronic obstructive pulmonary disease (COPD), changes in bronchial microvasculature are present in response to inflammatory stimuli. Vascular changes may significantly contribute to airway wall remodelling. Angiogenesis and vascular leakage are prevalent in asthma, while vasodilation and vascular leakage dominate in COPD. An endothelial dysfunction may be present both in asthma and in COPD. Vascular changes may occur simultaneously with the thickening of the airway wall and the narrowing of the bronchial lumen. Consequently, pharmacological control of bronchial vascular remodelling may be crucial for symptom control in asthma and COPD. In asthmatic airways, inhaled steroids can downregulate vascular remodelling by acting on proangiogenic factors. Additionally, studies on combination therapy with long-acting β2-agonists and inhaled steroids have provided evidence of a possible synergistic action on components of vascular remodelling in asthma. In COPD, there is less experimental evidence on the effect of inhaled steroids on airway microvascular changes. Importantly, vascular endothelial growth factor (VEGF), the most specific growth factor for vascular endothelium, is crucially involved in the pathophysiology of airway vascular remodelling, both in asthma and COPD. The inhibition of VEGF and its receptor may be useful in the treatment of the vascular changes in the airway wall.

Airway endothelial dysfunction in asthma and chronic obstructive pulmonary disease: a challenge for future research

Endothelial dysfunction in the extrapulmonary circulation has been linked to cardiovascular disease. Recent investigations have revealed that in the airway circulation, cigarette smoking, chronic obstructive pulmonary disease (COPD), and asthma are also accompanied by endothelial dysfunction. Inhaled glucocorticosteroids can partially or fully restore normal endothelium-dependent vasodilation in these conditions, thereby identifying the airway endothelium as a novel therapeutic target in the treatment of airway disease. The role of the defective endothelium-dependent vasodilation in the pathophysiology in asthma and COPD is still subject to speculation. However, there appears to be an association between COPD and extrapulmonary vascular dysfunction, and the possibility exists that the use of inhaled glucocorticosteroids has a beneficial effect on cardiovascular disease in COPD as suggested by database studies showing that inhaled glucocorticosteroids reduce the incidence of nonfatal and fatal cardiovascular events in COPD.

The bronchial circulation--worth a closer look: a review of the relationship between the bronchial vasculature and airway inflammation

Until recently, the bronchial circulation has been relatively ignored in the research and clinical arenas, perhaps because of its small volume and seeming dispensability relative to the pulmonary circulation. Although the bronchial circulation only receives around 1% of the cardiac output in health, it serves functions that are critical to maintaining airway and lung function. The bronchial circulation also plays an important role in many lung and airway diseases; through its ability to increase in size, the bronchial circulation is able to provide lung parenchymal perfusion when the pulmonary circulation is compromised, and more recently the role of the bronchial circulation in the pathogenesis of inflammatory airway disease has been explored. Due to the anatomic variability and small volume of the bronchial circulation, much of the research to date has necessitated the use of animal models and invasive procedures. More recently, non-invasive techniques for measuring bronchial blood flow in the mucosal microvascular network have been developed and offer a new avenue for the study of this circulation in humans. In conjunction with molecular research, measurement of airway blood flow (Q(aw)) may help elucidate the role of the bronchial circulation in inflammatory airway disease and become a useful tool for monitoring therapy.

Nitrite in exhaled breath condensate as a marker of nitrossative stress in the airways of patients with asthma, COPD, and idiopathic pulmonary fibrosis

BACKGROUND

Nitrite and nitrate are exhaled in droplets of an aerosol during breathing and can be assayed in the exhaled breath condensate (EBC) as markers of nitrossative stress in the airways of patients with asthma, COPD, and idiopathic pulmonary fibrosis (IPF).

SUBJECTS AND METHODS

Using HPLC with fluorescence detection, nitrite and nitrate were assayed in EBC of 14 atopic patients with mild-to-moderate stable asthma, 18 atopic asthmatics with exacerbation, 14 COPD patients without exacerbation, 18 patients with exacerbated COPD, 13 patients with active IPF, and in 29 healthy subjects.

RESULTS

The geometric mean [exp(mean±SD)] EBC concentrations of nitrite (micromol/l) in patients with asthma [5.1(2.1-12.3)], exacerbation of asthma [5.1(2.8-9.6)], exacerbation of COPD [5.3(3.2-8.7)], and with IPF [5.5(2.9-10.2)] were higher (P<0.05) compared with those of healthy subjects [2.9(1.6-5.3)] and patients with stable COPD [3.0(1.3-6.7)]. Nitrite concentration increased with decreased lung function of patients with asthma (r(s)=-0.31, P<0.02). Presumably owing to the contamination of the EBC sample with nitrate during collection, nitrate levels were highly variable among healthy subjects and higher compared with all groups of patients.

CONCLUSION

EBC nitrite is a suitable marker of nitrossative stress in adult patients with lung diseases but cannot differentiate controlled and exacerbated asthma. Further improvements to the methods of EBC collection and sample handling are warranted.