Effect of vitamin E on exhaled ethane in cigarette smokers

Biomarkers for differentiation of causes of respiratory distress in dogs and cats: Part 2--Lower airway, thromboembolic, and inflammatory diseases

OBJECTIVES

To review the current veterinary and relevant human literature regarding biomarkers of respiratory diseases leading to dyspnea and to summarize the availability, feasibility, and practicality of using respiratory biomarkers in the veterinary setting.

DATA SOURCES

Veterinary and human medical literature: original research articles, scientific reviews, consensus statements, and recent textbooks.

HUMAN DATA SYNTHESIS

Numerous biomarkers have been evaluated in people for discriminating respiratory disease processes with varying degrees of success.

VETERINARY DATA SYNTHESIS

Although biomarkers should not dictate clinical decisions in lieu of gold standard diagnostics, their use may be useful in directing care in the stabilization process. Serum immunoglobulins have shown promise as an indicator of asthma in cats. A group of biomarkers has also been evaluated in exhaled breath. Of these, hydrogen peroxide has shown the most potential as a marker of inflammation in asthma and potentially aspiration pneumonia, but methods for measurement are not standardized. D-dimers may be useful in screening for thromboembolic disease in dogs. There are a variety of markers of inflammation and oxidative stress, which are being evaluated for their ability to assess the severity and type of underlying disease process. Of these, amino terminal pro-C-type natriuretic peptide may be the most useful in determining if antibiotic therapy is warranted. Although critically evaluated for their use in respiratory disorders, many of the biomarkers which have been evaluated have been found to be affected by more than one type of respiratory or systemic disease.

CONCLUSION

At this time, there are point-of-care biomarkers that have been shown to reliably differentiate between causes of dyspnea in dogs and cats. Future clinical research is warranted to understand of how various diseases affect the biomarkers and more bedside tests for their utilization.

Smoking and atherosclerotic cardiovascular disease: part II: role of cigarette smoking in cardiovascular disease development

Potential mechanisms and biomarkers of atherosclerosis related to cigarette smoking - a modifiable risk factor for that disease - are discussed in this article. These include smoking-associated inflammatory markers, such as leukocytes, high-sensitivity C-reactive protein, serum amyloid A, ICAM-1 and IL-6. Other reviewed markers are indicative for smoking-related impairment of arterial endothelial function (transcapillary leakage of albumin, inhibition of endogenous nitric oxide synthase activity and reduced endothelium-dependent vasodilation) or point to oxidative stress caused by various chemicals (cholesterol oxidation, autoantibodies to oxidized low-density lipoprotein, plasma levels of malondialdehyde and F(2)-isoprostanes and reduced antioxidant capacity). Smoking enhances platelet aggregability, increases blood viscosity and shifts the pro- and antithrombotic balance towards increased coagulability (e.g., fibrinogen, von Willebrand factor, ICAM-1 and P-selectin). Insulin resistance is higher in smokers compared with nonsmokers, and hemoglobin A1c is dose-dependently elevated, as is homocysteine. Smoke exposure may influence the kinetics of markers with different response to transient or chronic changes in cigarette smoking behavior.

Antioxidant therapeutic advances in COPD

Chronic obstructive pulmonary disease (COPD) is associated with a high incidence of morbidity and mortality. Cigarette smoke-induced oxidative stress is intimately associated with the progression and exacerbation of COPD and therefore targeting oxidative stress with antioxidants or boosting the endogenous levels of antioxidants is likely to have beneficial outcome in the treatment of COPD. Among the various antioxidants tried so far, thiol antioxidants and mucolytic agents, such as glutathione, N-acetyl-L-cysteine, N-acystelyn, erdosteine, fudosteine and carbocysteine; Nrf2 activators; and dietary polyphenols (curcumin, resveratrol, and green tea catechins/quercetin) have been reported to increase intracellular thiol status along with induction of GSH biosynthesis. Such an elevation in the thiol status in turn leads to detoxification of free radicals and oxidants as well as inhibition of ongoing inflammatory responses. In addition, specific spin traps, such as alpha-phenyl-N-tert-butyl nitrone, a catalytic antioxidant (ECSOD mimetic), porphyrins (AEOL 10150 and AEOL 10113), and a SOD mimetic M40419 have also been reported to inhibit cigarette smoke-induced inflammatory responses in vivo in the lung. Since a variety of oxidants, free radicals and aldehydes are implicated in the pathogenesis of COPD, it is possible that therapeutic administration of multiple antioxidants and mucolytics will be effective in management of COPD. However, a successful outcome will critically depend upon the choice of antioxidant therapy for a particular clinical phenotype of COPD, whose pathophysiology should be first properly understood. This article will review the various approaches adopted to enhance lung antioxidant levels, antioxidant therapeutic advances and recent past clinical trials of antioxidant compounds in COPD.

The effects of dietary phenolic compounds on cytokine and antioxidant production by A549 cells

Levels of inflammatory cytokines are raised in chronic obstructive pulmonary disease (COPD). A diet rich in antioxidant vitamins may protect against the development of COPD. This study examined the effects of phenolic compounds and food sources on cytokine and antioxidant production by A549 cells. The effects of the following phenolic compounds on basal and interleukin (IL)-1-stimulated release of IL-8, IL-6, and reduced glutathione (GSH) were examined: resveratrol; Bouvrage, a commercially available raspberry juice (Ella Drinks Ltd., Alloa, Clacksmannanshire, UK); and quercetin 3'-sulfate. Purification of the raspberry juice by high-performance liquid chromatography gave three fractions: Fraction 1 contained phenolic acid and vitamin C, Fraction 2 contained flavonoids and ellagic acid, and Fraction 3 contained anthocyanins and ellagitannins. IL-8 production was increased in the presence of IL-1 (165 vs. 6,011 pg/mL, P < .0001). None of the compounds tested had any significant effect on GSH. Resveratrol at concentrations > or =50 micromol/mL significantly inhibited IL-8 and IL-6 production. Similar findings were made with raspberry juice at concentrations > or =25 microL/mL, and Fractions 1 and 3 were best able to inhibit IL-8 production. Quercetin 3'-sulfate, at 25 micromol/mL, inhibited IL-8 and IL-6 production. The changes observed in IL-8 were paralleled by changes in tumor necrosis factor-alpha. Thus, phenolic compounds can significantly alter cytokine and antioxidant production.

Airway biomarkers of the oxidant burden in asthma and chronic obstructive pulmonary disease: current and future perspectives

The pathogenesis of asthma and chronic obstructive pulmonary disease (COPD) has been claimed to be attributable to increased systemic and local oxidative stress. Detection of the oxidant burden and evaluation of their progression and phenotypes by oxidant biomarkers have proved challenging and difficult. A large number of asthmatics are cigarette smokers and smoke itself contains oxidants complicating further the use of oxidant biomarkers. One of the most widely used oxidant markers in asthma is exhaled nitric oxide (NO), which plays an important role in the pathogenesis of asthma and disease monitoring. Another oxidant marker that has been widely investigated in COPD is 8-isoprostane, but it is probably not capable of differentiating asthma from COPD, or even sensitive in the early assessment of these diseases. None of the current biomarkers have been shown to be better than exhaled NO in asthma. There is a need to identify new biomarkers for obstructive airway diseases, especially their differential diagnosis. A comprehensive evaluation of oxidant markers and their combinations will be presented in this review. In brief, it seems that additional analyses utilizing powerful tools such as genomics, metabolomics, lipidomics, and proteomics will be required to improve the specificity and sensitivity of the next generation of biomarkers.

Antioxidant therapies in COPD

Oxidative stress is an important feature in the pathogenesis of COPD. Targeting oxidative stress with antioxidants or boosting the endogenous levels of antioxidants is likely to be beneficial in the treatment of COPD. Antioxidant agents such as thiol molecules (glutathione and mucolytic drugs, such as N-acetyl-L-cysteine and N-acystelyn), dietary polyphenols (curcumin, resveratrol, green tea, catechins/quercetin), erdosteine, and carbocysteine lysine salt, all have been reported to control nuclear factor-kappaB (NF-κ B) activation, regulation of glutathione biosynthesis genes, chromatin remodeling, and hence inflammatory gene expression. Specific spin traps such as α-phenyl-N-tert-butyl nitrone, a catalytic antioxidant (ECSOD mimetic), porphyrins (AEOL 10150 and AEOL 10113), and a superoxide dismutase mimetic M40419 have also been reported to inhibit cigarette smoke-induced inflammatory responses in vivo. Since a variety of oxidants, free radicals, and aldehydes are implicated in the pathogenesis of COPD, it is possible that therapeutic administration of multiple antioxidants will be effective in the treatment of COPD. Various approaches to enhance lung antioxidant capacity and clinical trials of antioxidant compounds in COPD are discussed.

The Role of Oxidative Stress in the Pathogenesis??of COPD

Chronic inflammation and oxidative stress are important features in the pathogenesis of COPD. The increased oxidative stress in patients with COPD is the result of an increased burden of inhaled oxidants, as well as increased amounts of reactive oxygen species (ROS) generated by various inflammatory, immune and epithelial cells of the airways. Oxidative stress has important implications on several events of lung physiology and for the pathogenesis of COPD. These include oxidative inactivation of antiproteases and surfactants, mucus hypersecretion, membrane lipid peroxidation, mitochondrial respiration, alveolar epithelial injury, remodeling of extracellular matrix, and apoptosis. An increased level of ROS produced in the airways is reflected by increased markers of oxidative stress in the airspaces, sputum, breath, lungs, and blood in patients with COPD. The biomarkers of oxidative stress such as H2O2, F2-isoprostanes, malondialdehyde and 4-hydroxy-2-nonenal have been successfully measured in breath condensate. ROS and aldehydes play a key role in enhancing the inflammation through the activation of mitogen-activated protein kinases and redox-sensitive transcription factors such as nuclear factor kappa B and activator protein-1. Oxidative stress also alters nuclear histone acetylation and deacetylation leading to increased gene expression of pro-inflammatory mediators in the lung. Oxidative stress may play a role in the poor clinical efficacy of corticosteroids in the treatment of COPD. Since a variety of oxidants, free radicals, and aldehydes are implicated in the pathogenesis of COPD it is likely that a combination of antioxidants may be effective in the treatment of COPD. Antioxidant compounds may also be of therapeutic value in monitoring oxidative biomarkers indicating disease progression. Various approaches to enhance the lung antioxidant screen and the clinical effectiveness of antioxidant compounds in the treatment of COPD are discussed.

Oxidative stress in expired breath condensate of patients with COPD

OBJECTIVE

To evaluate the levels of hydrogen peroxide (H(2)O(2)) and 8-isoprostane in the expired breath condensate (EBC) of patients with COPD, and to assess the relationship between the above markers of oxidative stress and parameters expressing inflammatory process and disease severity.

SETTING

Inpatient respiratory unit and outpatient clinic in tertiary care hospital.

DESIGN

Cross-sectional study.

PATIENTS

Thirty stable COPD patients (all smokers) with disease severity ranging from mild to severe. Ten subjects who were smokers with stage 0 disease (ie, at risk for COPD; mean [+/- SD] FEV(1), 88 +/- 5% predicted) were studied as a control group.

METHODS

H(2)O(2) and 8-isoprostane levels were measured in EBC, and the values were correlated with variables expressing COPD severity (ie, FEV(1) percent predicted, dyspnea severity score (ie, Medical Research Council scale) and airway inflammation (ie, differential cell counts from induced sputum).

RESULTS

The mean concentration of H(2)O(2) was significantly elevated in COPD patients compared to control subjects (mean, 0.66 micromol/L [95% confidence interval (CI), 0.54 to 0.68 micro mol/L) vs 0.31 micro mol/L [95% CI, 0.26 to 0.35 micromol/L], respectively; p < 0.0001). The difference was primarily due to the elevation of H(2)O(2) in patients with severe and moderate COPD, whose expired breath H(2)O(2) levels were significantly higher than those of patients with mild disease (mean, 0.96 micromol/L [95% CI, 0.79 to 1.13 micromol/L], 0.68 micromol/L [95% CI, 0.55 to 0.81 micromol/L], and 0.33 micromol/L [95% CI, 0.24 to 0.43 micromol/L], respectively, p < 0.0001). The mean concentration of 8-isoprostane was significantly elevated in patients with COPD compared to that of the control group (47 pg/mL [95% CI, 41 to 53 pg/mL] vs 29 pg/mL [95% CI, 25 to 33 pg/mL], respectively; p < 0.0001) but did not differ significantly among the different stages of the disease (p = 0.43). Repeatability and stability data within measurements showed that H(2)O(2) has a better repeatability and stability than 8-isoprostane. Furthermore, we observed significant correlations of H(2)O(2) with FEV(1), neutrophil count, and dyspnea score. Those correlations existed only in patients with moderate and severe disease. No correlations were found between levels of 8-isoprostane and the above parameters.

CONCLUSIONS

We conclude that levels of H(2)O(2) and 8-isoprostane are elevated in the EBC of patients with COPD, but that H(2)O(2) seems to be a more repeatable and a more sensitive index of the inflammatory process and the severity of the disease.

Elevated urinary 8-hydroxydeoxyguanosine, a biomarker of oxidative stress, and lack of association with antioxidant vitamins in chronic obstructive pulmonary disease

OBJECTIVE

The purpose of this study was to investigate whether patients with COPD are under oxidative stress and to elucidate the relationship between the level of oxidative stress and antioxidant vitamins.

METHODOLOGY

Nineteen male patients with COPD and 13 age- matched male control subjects were studied. Urinary 8-hydroxydeoxyguanosine (8-OHdG) concentrations were determined using an enzyme-linked immunosorbent assay kit and corrected for creatinine concentrations. Serum levels of vitamin C, alpha-tocopherol, and beta-carotene were determined by high performance liquid chromatography.

RESULTS

The median (interquartile range) 8-OHdG excretion was 8.1 ng/mg (5.3-10.9 ng/mg) in control subjects and 12.2 ng/mg (9.8-15.5 ng/mg) in COPD patients (P < 0.01). Urinary 8-OHdG levels were significantly elevated in ex-smokers in the COPD group compared with ex-smokers in the control group. Urinary 8-OHdG level was negatively correlated with FVC (r = -0.42, P = 0.016), FEV1 (r = -0.49, P = 0.0048), and oxygen tension in arterial blood (r = -0.41, P = 0.0005). No significant differences in antioxidant levels were demonstrated between the two groups. There were no significant correlations between urinary 8-OHdG excretion and the serum concentrations of antioxidant vitamins.

CONCLUSION

The burden of oxidative stress was observed to increase in COPD patients as judged by urinary 8-OHdG. A depletion of antioxidant vitamins in serum was not essential for this phenomenon. Elevated urinary 8-OHdG level may not be attributable to smoking status or to antioxidant vitamins in COPD.

Oxidative stress and smoking-induced vascular injury

The relative importance of mechanisms relevant to smoking-induced vascular injury is poorly understood. Cigarette smoke is a source of free radicals but also results in cellular activation and consequent generation of free radicals in vivo. Here we consider several approaches to estimating the consequences of free radical generation in vivo, using measurements of modified lipids, proteins, and DNA. Smoking appears to result in elevation of several biomarkers of oxidant stress, some in a dose-related fashion. There is also some evidence that disordered endothelial function in smokers may be partly attributable to oxidant stress. Other effects of smoking on hemostatic activation, sympathoadrenal function, and lipoprotein structure and function may also be modulated by smoking-induced oxidant stress. The emergence and application of rational quantitatively reliable indexes of oxidant stress in vivo is likely to elucidate the relative contribution of oxidant stress to smoking-induced vascular injury.

Effects of exogenous vitamin E supplementation on the levels of oxidants and antioxidants in chronic obstructive pulmonary disease

Oxidative stress has been recognized as a central feature of smoke induced chronic obstructive pulmonary disease (COPD). Imbalance between oxidant and antioxidant enzymes is also an established fact in these patients. But studies in regard to stable COPD patients and effect of vitamin E supplementation are lacking. Thirty patients with COPD were included in the study. Their baseline clinical examination, spirometry, plasma malondialdehyde (MDA), alpha-tocopherol and red blood cell superoxide dismutase (SOD) levels were mea sured. Twenty healthy non-smokers who were matched for age and sex served as controls. All the above parameters were repeated after 12 weeks of supplementation with 400 IU of vitamin E daily. The mean malondialdehyde levels in the patients at baseline were higher than controls (5.91 +/- 1.23 nmol/ml vs 4.55 +/- 1.51 nmol/ml, P = 0 001), so also was plasma alpha-tocopherol levels (P < 0 001), while SOD levels were lower in the patients compared to controls (1692 +/- 259 units g/Hb vs 2451 +/- 131 units g/Hb, P < 0 001). Exogenous vitamin E (400 IU per day) supplementation did not bring about any significant change in plasma alpha-tocopherol and SOD levels. The Pearson s co-efficient of correlation between the levels of MDA, vitamin E, SOD; and spirometric measurements were not significant either on day 1 or after 12 weeks of vitamin E supplementation. The present study shows that initially the plasma lipid peroxide (MDA) levels are high and antioxidants (alpha-tocopherol and SOD) are low in patients with COPD. Exogenous supplementation with vitamin E does not have any significant effect on the spirometric measurements though it brings down the levels of MDA showing attenuation of further damage. However, inclusion of larger number of patients and supple mentation with vitamin E for longer periods may throw more light on free radical injury and protective effects of antioxidants.

Analysis of expired air for oxidation products

Chronic inflammation is a critical feature of chronic obstructive pulmonary disease, cystic fibrosis, and asthma. This inflammation is associated with the increased production of reactive oxygen species or oxidative stress in the lungs. Oxidative stress may have several adverse effects and may amplify the inflammatory process; however, monitoring oxidative stress is difficult and may not be reflected by changes in blood markers. We have therefore developed several noninvasive markers in the exhaled breath that may indicate oxidative stress in the lungs, and we studied these in relationship to the severity of chronic inflammatory lung diseases. We analyzed the exhaled breath for the content of nitric oxide as a marker of inflammation, carbon monoxide as a marker of oxidative stress, and ethane, which is one of the end products of lipid peroxidation. In addition, we measured the concentration of markers of oxidative stress such as isoprostanes in exhaled breath condensate. Our results confirm that there are increased inflammation, oxidative stress, and lipid peroxidation in lung disease, as shown by elevated levels of nitric oxide, carbon monoxide, and ethane, respectively. The finding of lower levels of these gases in patients on steroid treatment and of higher levels in those with more severe lung disease, as assessed by lung function tests and clinical symptoms, reinforces the hypothesis that the noninvasive measurement of exhaled gases maybe useful in monitoring the underlying pathologic pathways of lung disease. Longitudinal studies are required to assess the clinical usefulness of these measurements in the monitoring of chronic inflammatory lung disease.

"Haemoxygenase-1 induction and exhaled markers of oxidative stress in lung diseases", summary of the ERS Research Seminar in Budapest, Hungary, September, 1999

In recent years, there has been increasing interest in noninvasive monitoring of airway inflammation and oxidative stress. Several volatile and nonvolatile substances can be measured in exhaled breath and have been suggested as potential biomarkers of these events. Exhaled gases, including carbon monoxide (CO), alkanes (ethane, pentane), and substances measured in breath condensate, such as hydrogen peroxide (H2O2) and isoprostanes were all suggested as potential markers of oxidative stress in the lung. A European Respiratory Society (ERS) International Research Seminar entitled "Haemoxygenase-1 induction and exhaled markers of oxidative stress in lung diseases" was organized by the Airway Regulation and Provocation Group of the Clinical Allergy and Immunology Assembly in Budapest, Hungary in September, 1999 to integrate the latest knowledge on these issues and accelerate further improvement in this area. During this 2-day event several issues were raised about: the use and standardization of measurements in exhaled breath; problems of measuring expired H2O2 and other mediators in breath condensate; role and regulation of haemoxygenase (HO)-1 in the lung; and conditions and factors influencing exhaled CO. This report is a summary of the main presentations at the seminar, together with the current areas of research in this rapidly expanding field.

Pro-oxidant effect of vitamin E in cigarette smokers consuming a high polyunsaturated fat diet

Dietary polyunsaturated fats and vitamin E are associated with reduced risk for atherosclerosis, but in smokers, they could promote lipid oxidation. Therefore, we examined the effects of a high polyunsaturated fat diet and vitamin E supplementation on measures of lipid oxidation in cigarette smokers. Ten subjects who smoked >1 pack of cigarettes per day were sequentially fed the following: a baseline diet in which the major fat source was olive oil, a diet in which the major fat source was high-linoleic safflower oil, and finally, the safflower oil diet plus 800 IU vitamin E per day. LDL oxidation lag time and rate and plasma total F(2)-isoprostanes and prostaglandin F(2alpha) (PGF(2alpha)) were determined after 3 weeks on each diet. The safflower oil diet increased total F(2)-isoprostanes from 53.0+/-7.2 to 116.2+/-11.2 nmol/L and PGF(2alpha) from 3.5+/-0.2 to 5.5+/-0.5 nmol/L, without changing LDL oxidation parameters. Addition of vitamin E prolonged mean LDL oxidation lag time but, paradoxically, further increased F(2)-isoprostanes to 188.2+/-10.9 nmol/L and PGF(2alpha) to 7.8+/-0.4 nmol/L. These data suggest that vitamin E may function as a pro-oxidant in cigarette smokers consuming a high polyunsaturated fat diet.

Exhaled ethane, a marker of lipid peroxidation, is elevated in chronic obstructive pulmonary disease

Ethane is a product of lipid peroxidation and can be measured in the exhaled air as an index of oxidative stress. Oxidant/antioxidant imbalance is important in the pathogenesis of chronic obstructive pulmonary disease (COPD). Therefore, we measured exhaled ethane in 22 patients with COPD (mean age +/- SEM, 59 +/- 8 yr; 19 male) and compared it with other noninvasive markers of oxidative stress and inflammation such as carbon monoxide (CO), measured electrochemically, and nitric oxide (NO), measured by chemiluminescence. Exhaled ethane was collected during a flow and pressure-controlled exhalation into a reservoir, discarding dead space air contaminated with ambient air. A sample of the collected expired air was analyzed by chromatography. Compared with normal subjects (n = 14; eight men; age, 33 +/- 2.8 yr), patients with COPD not on steroid treatment (n = 12; FEV(1), 58 +/- 6%) had elevated levels of exhaled ethane (2.77 +/- 0.25 and 0.88 +/- 0.09 ppb, respectively, p < 0.05), CO (5.96 +/- 0.50 and 2.8 +/- 0.25 ppm, p < 0.05) and NO (11.86 +/- 0.53 and 6.77 +/- 0.50 ppb, p < 0.05) levels. Ethane was correlated to FEV(1) (r = -0.67, p < 0.05). Patients receiving steroid treatment (n = 10; FEV(1), 56 +/- 2%) had lower levels of ethane (0.48 +/- 0.05 ppb) than did steroid-treated patients, whereas CO (5.99 +/- 0.63 ppm) and NO (9.11 +/- 0.53 ppb) levels were similar in the two treatment groups. Exhaled ethane is elevated, correlates with FEV(1), and is significantly lower in patients treated with steroids, so it may be complementary to the use of NO and CO in assessing and monitoring oxidative stress in COPD.

Exhaled ethane is elevated in cystic fibrosis and correlates with carbon monoxide levels and airway obstruction

Ethane is produced from lipid peroxidation and can be measured in the exhaled air. Cystic fibrosis (CF) is characterized by recurrent respiratory infections, release of reactive oxygen species by inflammatory cells, and increased oxidative stress. We measured exhaled ethane in 23 CF subjects (mean age +/- SEM, 21 +/- 4 yr; 10 male, FEV(1) 62 +/- 4%) and compared it with two other noninvasive markers of oxidative stress and inflammation, carbon monoxide (CO) and nitric oxide (NO). Exhaled ethane was collected during a flow and pressure-controlled exhalation into a reservoir discarding dead space air contaminated with ambient air. A sample (2 ml) of the expired air was analyzed by chromatography. Ethane levels were elevated in patients not on steroids (n = 13, 1.99 +/- 0.20 ppb) compared with steroid-treated patients (n = 10, 0.67 +/- 0.09 ppb, p < 0.01) and with 14 nonsmoking control (8 men, age 33 +/- 2.8 yr) subjects (0.82 +/- 0.40 ppb, p < 0.05). In patients not on steroid treatment ethane was correlated to airway obstruction as assessed by the ratio of residual volume to total lung capacity (RV/ TLC) (r = 0. 66, p < 0.05) and exhaled CO (r = 0.65, p < 0.05). CO concentrations were also higher in patients not on steroid treatment (3.4 +/- 0.2 ppm) than in steroid-treated patients (2.6 +/- 0.1 ppm, p < 0.05), whereas NO concentrations were not influenced by steroid treatment (3.0 +/- 0.4 ppm and 2.9 +/- 0.2 ppm, p > 0.05) and were lower than in a control group (7.0 +/- 0.4 ppb, p < 0.05). Exhaled ethane is elevated in CF, reduced in steroid-treated patients and correlates with CO and RV/TLC; therefore, it may be a useful noninvasive marker of oxidative stress.

Is there any relationship between plasma antioxidant capacity and lung function in smokers and in patients with chronic obstructive pulmonary disease?

BACKGROUND

It has been suggested that oxidative stress is an important factor in the pathogenesis of chronic obstructive pulmonary disease (COPD). We have shown that an oxidant/antioxidant imbalance occurs in the distal air spaces of smokers and in patients with COPD which is reflected systemically in the plasma. A study was undertaken to determine whether plasma antioxidant status correlated with lung function as assessed by forced expiratory volume in one second (FEV(1)) and forced vital capacity (FVC) in smokers and patients with COPD.

METHODS

Plasma antioxidant capacity, assessed by the Trolox equivalent antioxidant capacity (TEAC) as an index of overall systemic oxidative stress, and protein thiol levels were measured in 95 patients with stable COPD, in 82 healthy smokers, and in 37 healthy non-smokers.

RESULTS

Mean (SE) plasma TEAC levels were significantly decreased in patients with COPD (0.81 (0.03) mmol/l, p<0.001) and in healthy smokers (0.87 (0.04) mmol/l, p<0. 001) compared with healthy non-smokers (1.31 (0.11) mmol/l). The mean differences in plasma antioxidant capacity (mM) were (0.81, 95% confidence interval (CI) 0.22 to 1.48), (0.87, 95% CI 0.2 to 1.46), and (1.31, 95% CI 1.09 to 1.58) in patients with COPD, healthy smokers, and healthy non-smokers, respectively. This reduction was associated with a 29% (95% CI 18 to 38) and a 30% (95% CI 19 to 40) decrease in plasma protein thiol levels in COPD patients and smokers, respectively. Current smoking was not the main contributor to the reduction in antioxidant capacity in patients with COPD as those patients who were still smokers had similar TEAC levels (mean (SE) 0. 78 (0.05); n = 25) to those who had stopped smoking (0.84 (0.02); n = 70). No significant correlations were found between spirometric data measured as FEV(1) % predicted or FEV(1)/FVC % predicted and the plasma levels of TEAC in patients with COPD, healthy smokers, or healthy non-smokers. Similarly, there was no significant correlation between FEV(1) % predicted or FEV(1)/FVC % predicted and the levels of plasma protein thiols in the three groups.

CONCLUSIONS

These data confirm decreased antioxidant capacity in smokers and patients with COPD, indicating the presence of systemic oxidative stress. However, no relationship was found between protein thiols or TEAC levels and measurements of airflow limitation in either smokers or in patients with COPD.

Methods for measuring ethane and pentane in expired air from rats and humans

Numerous studies in animals and humans provide evidence that ethane and pentane in expired air are useful markers of in vivo lipid peroxidation. The measurement of breath hydrocarbons, being noninvasive, is well suited for routine use in research and clinical settings. However, the lack of standardized methods for collecting, processing, and analyzing expired air has resulted in the use of a wide variety of different methods that have yielded highly disparate results among investigators. This review outlines the methods that we have developed and validated for measuring ethane and pentane in expired air from rats and humans. We describe the advantages of these methods, their performance, as well as potential errors that can be introduced during sample collection, concentration, and analysis. A main source of error involves contamination with ambient-air ethane and pentane, the concentrations of which are usually much greater and more variable than those in expired air. Thus, it appears that the effective removal of ambient-air hydrocarbons from the subject's lungs before collection is an important step in standardizing the collection procedure. Also discussed is whether ethane or pentane is a better marker of in vivo lipid peroxidation.