Lipid peroxidation as determined by plasma isoprostanes is related to disease severity in mild asthma

Exhaled cysteinyl-leukotrienes and 8-isoprostane in patients with asthma and their relation to clinical severity

BACKGROUND

Collection of exhaled breath condensate (EBC) is a safe, non-invasive method to collect droplets of the airway surface liquid and measure mediators of airway inflammation and oxidative stress, such as cysteinyl-leukotrienes (cys-LTs) and 8-isoprostane.

OBJECTIVE

The aim of our study was to investigate baseline values of inflammatory lipid mediators in EBC and their relation to asthma severity.

METHODS

Nineteen healthy subjects, 16 mild, 12 moderate and 15 severe asthmatics were studied. All subjects attended a clinic visit for spirometry and EBC collection. The concentrations of exhaled cys-LTs and 8-isoprostane were measured by means of specific enzyme immunoassays.

RESULTS

8-isoprostane levels were significantly increased in mild (49.1+/-5.2 pg/mL, p<0.001), moderate (49.7+/-5.2 pg/mL, p<0.001) and severe asthmatics (77.7+/-7.3 pg/mL, p<0.001), compared to healthy controls (16.4+/-1.6 pg/mL). Moreover, 8-isoprostane levels were significantly higher in severe compared to mild and moderate asthmatics (p<0.01). Cys-LT levels were significantly higher in moderate (34.6+/-4.4 pg/mL, p<0.05) and severe asthmatics (47.9+/-6.0 pg/mL, p<0.001), while no significant difference was found between healthy controls and mild asthmatics. 8-isoprostane levels in EBC of asthmatics strongly correlated with cys-LT levels (r=0.61, p<0.0001).

CONCLUSIONS

8-isoprostane and cys-LT are detectable in EBC of healthy subjects and their levels progressively increase in asthmatic patients according to disease severity. The correlation found between these two lipid mediators indicating a link between oxidative stress and airway inflammation.

Role of Ca2+ mobilization and Ca2+ sensitization in 8-iso-PGF 2 alpha-induced contraction in airway smooth muscle

BACKGROUND

Isoprostanes are prostaglandin (PG)-like compounds synthesized by oxidative stress, not by cyclooxygenase, and increase in bronchoalveolar lavage fluid of patients with asthma. The airway inflammation implicated in this disease may be amplified by oxidants. Although isoprostanes are useful biomarkers for oxidative stress, the action of these agents on airways has not been fully elucidated.

OBJECTIVE

This study was designed to determine the intracellular mechanisms underlying the effects of oxidative stress on airway smooth muscle, focused on Ca(2+) signalling pathways involved in the effect of 8-iso-PGF(2 alpha).

METHODS

Using simultaneous recording of isometric tension and F(340)/F(380) (an indicator of intracellular concentrations of Ca(2+), [Ca(2+)]i, we examined the correlation between tension and [Ca(2+)]i in response to 8-iso-PGF(2 alpha) in the fura-2 loaded tracheal smooth muscle.

RESULTS

Augmented tension and F(340)/F(380) by 8-iso-PGF(2 alpha) were attenuated by ICI-192605, an antagonist of thromboxane A(2) receptors (TP receptors). Moreover, D609, an antagonist of phosphatidylcholine-specific phospholipase C, markedly reduced both the tension and F(340)/F(380) induced by 8-iso-PGF(2 alpha), whereas U73122, an antagonist of phosphatidylinositol-specific phospholipase C, modestly inhibited them by 8-iso-PGF(2 alpha). SKF96365, a non-selective antagonist of Ca(2+) channels, markedly reduced both tension and F(340)/F(380) by 8-iso-PGF(2 alpha). However, diltiazem and verapamil, voltage-dependent Ca(2+) channel inhibitors, modestly attenuated tension although their reduction of F(340)/F(380) was not different from that by SKF96365. Y-27632, an inhibitor of Rho-kinase, significantly attenuated contraction induced by 8-iso-PGF(2 alpha) without reducing F(340)/F(380), whereas GF109203X and Go6983, protein kinase C inhibitors, did not markedly antagonize them although reducing F(340)/F(380) with a potency similar to Y-27632.

CONCLUSION

8-iso-PGF(2 alpha) causes airway smooth muscle contraction via activation of TP receptors. Ca(2+) mobilization by SKF96365- and D609-sensitive Ca(2+) influx and Ca(2+) sensitization by Rho-kinase contribute to the intracellular mechanisms underlying the action of 8-iso-PGF(2 alpha). Rho-kinase may be a therapeutic target for the physiologic abnormalities induced by oxidative stress in airways.

F2-isoprostanes in human health and diseases: from molecular mechanisms to clinical implications

Oxidative stress is implicated as one of the major underlying mechanisms behind many acute and chronic diseases, and involved in normal aging. However, the measurement of free radicals or their end products is complicated. Thus, proof of association of free radicals in pathologic conditions has been absent. Isoprostanes are prostaglandin-like bioactive compounds that are biosynthesized in vivo independent of cyclooxygenases, principally through free-radical catalyzation of arachidonic acid. Isoprostanes are now considered to be reliable biomarkers of oxidative stress, as evidenced by an autonomous study organized recently by the National Institutes of Health (NIH) in the United States. A number of these compounds have potent biologic activities such as vasoconstrictive and certain inflammatory properties. Isoprostanes are involved in many human diseases. Additionally, elevated levels of F(2)-isoprostanes have been seen in normal human pregnancy and after intake of some fatty acids, but their physiologic assignments have not yet been distinctive. This evidence indicates that measurement of bioactive F(2)-isoprostanes in body fluids offers a unique noninvasive analytic utensil to study the role of free radicals in physiology, oxidative stress-related diseases, experimental acute or chronic inflammatory conditions, and also in the assessment of various antioxidants, radical scavengers, and drugs.

The value of sputum 8-isoprostane in detecting oxidative stress in mild asthma

BACKGROUND

Exhaled nitric oxide and induced sputum eosinophils are well established as direct markers of inflammation/oxidative stress in asthma. Recently, it has been proposed that sputum 8-isoprostane concentrations may present a reliable index for measuring oxidative stress in asthmatic patients. We assessed the value of sputum 8-isoprostane in mild asthma in children and adolescents.

METHODS

Patients with newly diagnosed asthma (children, n = 23; adults, n = 14) and age-matched healthy controls (children, n = 13; adults, n = 15) were studied. Lung function was measured by spirometry, sputum was induced by hypertonic saline, and fractional exhaled nitric oxide (FeNO) was measured with standard methods. Cell differential counts were obtained from sputum slides and the concentration of 8-isoprostane was measured with an enzyme immunoassay from sputum supernatants.

RESULTS

High-quality sputum specimens could be obtained from 10 children and 10 adults, and the sputum analyses were conducted only for the representative specimens. Asthmatics had increased FeNO (children 35.5 vs. 11.9 ppb; adults 81.1 vs. 16.6 ppb; p < 0.001) and sputum eosinophils (children 2.4% vs. 1.4%; adults 10.4% vs. 0.2%; p = 0.005) compared to healthy controls. There was a significant correlation between FeNO and eosinophils (R = 0.65; p < 0.0001). Sputum 8-isoprostane was not elevated in asthmatics compared to healthy subjects (children 81.1 vs. 89.9 and adults 76.9 vs. 73.4 pg/mL) and did not correlate with lung function or other measurements of airway inflammation. However, increased 8-isoprostane levels were detected in patients with chronic obstructive pulmonary disease (n = 11, 184.7 pg/mL, used as controls for assays).

CONCLUSIONS

In agreement with earlier studies, FeNo is sensitive in detecting oxidative/nitrosative stress in asthmatic airways. However, our results suggest that 8-isoprostane may not be sensitive in reflecting oxidant burden in mild asthma.

Redox-based therapeutics for lung diseases

Because oxidative stress is such a common factor of lung diseases, we cannot help asking why so many diseases are caused by the same oxidative stress. It is likely to be a consequence of diversity in sources and location of oxidative stress, and concomitant factors. The aim of this forum is to characterize the disease-specific involvement of oxidative stress and to make use of it for therapeutics. It is also of note that oxidative-stress biomarkers are useful tools for disease management. Exhaled nitric oxide has been established as a marker of bronchial asthma in clinical practice. By using recent noninvasive techniques, such as exhaled breath condensate, other markers of lipid peroxidation or antioxidants are now under evaluation. Antioxidant therapy, as represented by N-acetylcysteine, has widely been tested as a treatment for lung disorders, but it has had limited success in clinical practice. The clinical outcome might be improved by combination therapy or better patient selection. Novel antioxidant drugs are also under investigation. Molecular targeted therapy against redox-sensitive signaling pathways could be an alternative therapeutic approach. Moreover, disease-specific pathways have been identified whose regulation could be more efficient and less toxic than regulating universal pathways.

Effects of chronic L-NAME treatment lung tissue mechanics, eosinophilic and extracellular matrix responses induced by chronic pulmonary inflammation

The importance of lung tissue in asthma pathophysiology has been recently recognized. Although nitric oxide mediates smooth muscle tonus control in airways, its effects on lung tissue responsiveness have not been investigated previously. We hypothesized that chronic nitric oxide synthase (NOS) inhibition by N(omega)-nitro-L-arginine methyl ester (L-NAME) may modulate lung tissue mechanics and eosinophil and extracellular matrix remodeling in guinea pigs with chronic pulmonary inflammation. Animals were submitted to seven saline or ovalbumin exposures with increasing doses (1 approximately 5 mg/ml for 4 wk) and treated or not with L-NAME in drinking water. After the seventh inhalation (72 h), animals were anesthetized and exsanguinated, and oscillatory mechanics of lung tissue strips were performed in baseline condition and after ovalbumin challenge (0.1%). Using morphometry, we assessed the density of eosinophils, neuronal NOS (nNOS)- and inducible NOS (iNOS)-positive distal lung cells, smooth muscle cells, as well as collagen and elastic fibers in lung tissue. Ovalbumin-exposed animals had an increase in baseline and maximal tissue resistance and elastance, eosinophil density, nNOS- and iNOS-positive cells, the amount of collagen and elastic fibers, and isoprostane-8-PGF(2alpha) expression in the alveolar septa compared with controls (P<0.05). L-NAME treatment in ovalbumin-exposed animals attenuated lung tissue mechanical responses (P<0.01), nNOS- and iNOS-positive cells, elastic fiber content (P<0.001), and isoprostane-8-PGF(2alpha) in the alveolar septa (P<0.001). However, this treatment did not affect the total number of eosinophils and collagen deposition. These data suggest that NO contributes to distal lung parenchyma constriction and to elastic fiber deposition in this model. One possibility may be related to the effects of NO activating the oxidative stress pathway.

Nutrition in pediatric lung disease

The respiratory system exists in an oxygenated milieu and is recurrently exposed to both endogenous and exogenous oxidants and irritants. A variety of dietary-dependent defenses have evolved to protect the lungs. These comprise vitamins, proteins, polyphenols, fatty acids and co-factors. This is a brief review of oxidant sources and the antioxidant system, as pertains to the respiratory system. The challenge to both clinicians and investigators is to understand how defenses are integrated and coordinated so that enhanced protection can be delivered.

A biopsychosocial approach to examining tobacco-related health disparities among racially classified social groups

AIMS

To articulate a broader, multi-causal model that incorporates psychosocial and environmental factors that can differ systematically across racially classified social groups (RCSGs) and impact biological pathways related to the development of tobacco-related diseases.

METHODS

This paper is built upon a review of the existing scientific literature on selected biopsychosocial factors (diet/nutrition, obesity, alcoholic intake, psychosocial stress, occupational/environmental exposures and exposure to other diseases and illnesses) and tobacco use in examining the biological contributions to differences in tobacco-related health outcomes among RCSGs.

FINDINGS

Recent work has focused on RCSG genetic variations as a possible explanation for differences in tobacco-related health disparities. It is argued in this paper that, given the genetic heterogeneity 'within' RCSGs, it is unlikely that across RCSG genetic variations are likely to be the major source of differences impacting biological pathways in tobacco-related health outcomes. The evidence shows that results, even at the level of within-population genetic variations, have been limited and often inconsistent. A conceptual framework is proposed to account for biological pathways related to the development of tobacco-related diseases.

CONCLUSIONS

Determinants of tobacco-related health disparities are not understood clearly. The contribution of biological factors may be important. Current efforts to determine biological differences in tobacco use and related diseases among RCSGs have focused primarily on genetic variations. However, this approach has limitations. An alternative biopsychosocial framework that examines the potential biological mechanisms through which life experiences and behavior might affect tobacco use and health outcomes in these population groups is needed, including those of life-style (e.g. diet/nutrition, obesity, physical exercise, alcohol consumption), psychosocial (e.g. stress and coping), occupational/environmental exposures and the presence of other diseases/illnesses.

Lipid peroxides in stable asthmatics receiving inhaled steroids and long-acting beta2 -agonists

BACKGROUND AND OBJECTIVE

The effect of inhaled steroids on oxidative stress in asthmatics is unclear. The levels of lipid peroxides in the serum of asthmatic patients, whose symptoms were controlled with inhaled corticosteroids and long-acting beta(2)-agonists, were measured in this study.

METHODS

Twenty asthmatic patients and 17 matched, healthy controls were recruited. Oxidative stress levels were quantified by measuring thiobarbituric acid reactive substances.

RESULTS

After 3 months of treatment, the mean lipid peroxide concentrations were significantly higher in asthmatic patients than in the healthy controls (4.2 +/- 0.13 micromol/mL vs. 3.6 +/- 0.07 micromol/mL, respectively).

CONCLUSION

The level of lipid peroxides is higher in patients with asthma than in healthy controls, even when the asthma is well controlled after 3 months of treatment. A longer period of therapy may be required before lipid peroxidation normalizes.

Salivary oxidative stress in children during acute asthmatic attack and during remission

BACKGROUND

Patients with asthma generate an increased amount of reactive oxygen species from peripheral blood cells, which may contribute to its pathogenesis. Saliva analysis is non-invasive and friendly to children. We undertook this study to analyze the salivary oxidative profile and composition in children with asthma during attack and remission, and to compare them with the levels of salivary antioxidants of healthy control children.

METHODS

School age (range 6-18 years) children referred to the emergency room for acute asthma were included. Clinical score was assessed, spirometry performed, and saliva samples were collected and analyzed. All measurements were repeated during remission of asthma attack (2-4 weeks after attack). Salivary analysis was performed blindly during asthma attack and the results were compared to those obtained during remission, and to those of the control group.

RESULTS

Statistically significant decreases in levels of salivary peroxidase enzyme activity were observed in asthmatic children during attack compared with healthy controls, with partial recovery during remission of attack. Similarly decreased levels of calcium concentrations were observed in asthmatic children, accompanied by increased phosphate levels.

CONCLUSIONS

Children with acute asthma attacks exhibit a decrease in the activity of the most important salivary antioxidant enzyme-peroxidase, which is accompanied by other salivary composition alterations. Hence, acute asthma is manifested by salivary changes. This implies systemic oxidative stress in asthma, which may be reflected in salivary analysis.

Pharmacological actions of isoprostane metabolites and phytoprostanes in human and bovine pulmonary smooth muscles

We examined the responses to various isoprostane derivatives in bovine/human airway and pulmonary arteries. All biological activity of 15-F(2t)-IsoP was lost in its two major metabolites (15-keto-15-F(2t)-IsoP and 13,14-dihydro-15-keto-15-F(2t)-IsoP). We also examined the effects of several metabolites of 15-F(2t)-IsoP synthesized within our own laboratory-both epimers of 2,3-dinor-15-F(2t)-IsoP and of 2,3-dinor-5,6-dihydro-15-F(2t)-IsoP, as well as 20-carboxy-2,3,4,5-tetranor-15 oxo-5,6,13,14-tetrahydro-15-F(2t)-isoP)-finding none of these to have any substantial excitatory effect. Finally, several plant-derived isoprostanes ("phytoprostanes") synthesized within our laboratory elicited little or no excitatory response in these three pulmonary smooth muscle preparations. We conclude that, although isoprostane exhibit powerful constrictor effects on airway and pulmonary vascular smooth muscles, metabolic processing of those isoprostanes essentially abolishes those biological actions; also, the phytoprostanes lack any appreciable pharmacological activity on those smooth muscle preparations.

Oxidative stress in children receiving valproic acid

OBJECTIVE

To determine whether valproic acid (VPA) influences urinary levels of 15-F2t -isoprostane (15-F2t -IsoP), a marker of oxidative stress, in children.

STUDY DESIGN

Morning urine samples were collected from children with epilepsy receiving VPA (n = 25), carbamazepine (n = 16), or clobazam (n = 12) for > or = 4 weeks and from age-matched control subjects (n = 39). Urinary 15-F2t -IsoP levels were determined by enzyme-linked immunosorbent assay.

RESULTS

The mean (+/- standard deviation) urine 15-F2t -IsoP levels (nmol/mmol Cr) were: valproic acid (0.36 +/- 0.15); carbamazepine (0.24 +/- 0.10); clobazam (0.23 +/- 0.10); control group (0.20 +/- 0.09). Patients treated with VPA had significantly elevated 15-F2t -IsoP levels when compared with the control, carbamazepine, and clobazam groups (P < .05). Multiple linear regression analysis demonstrated that younger patient age and exposure to second-hand smoke were significant predictors of elevated urine 15-F2t -IsoP levels within the control group (r2 = 0.261, P = .05 and P = .01, respectively). Subjects not exposed to second-hand smoke receiving valproic acid therapy had a significantly elevated mean urine 15-F2t -IsoP level compared to subjects not exposed to second-hand smoke in the carbamazepine, clobazam and control groups (P < .05).

CONCLUSIONS

These data demonstrate that treatment of children with VPA is associated with higher urinary levels of 15-F2t -IsoP, a marker of oxidative stress.

Maternal antioxidant intake in pregnancy and wheezing illnesses in children at 2 y of age

BACKGROUND

Low intakes of dietary antioxidants may contribute to increases in asthma and allergy.

OBJECTIVE

We investigated the association of maternal total intakes (foods + supplements) of 10 antioxidant nutrients during pregnancy with wheezing and eczema in 2-y-old children.

DESIGN

Subjects were 1290 mother-child pairs in an ongoing cohort study. Maternal dietary and supplement intakes were assessed by using a validated food-frequency questionnaire administered in the first and second trimesters. Antioxidant nutrient intakes were calculated, and the mean for each nutrient was considered to be the exposure during pregnancy. The outcomes of interest were any wheezing by the child during either the first or second year of life, recurrent wheezing in both years, and eczema in either the first or second year.

RESULTS

No association was observed between maternal total intake of any antioxidant nutrient and eczema. In multivariate logistic regression models, the highest quartile compared with the lowest quartile of maternal total intakes of vitamin E [odds ratio (OR): 0.70; 95% CI: 0.48, 1.03] and zinc (OR: 0.59; 95% CI: 0.41, 0.88) was inversely associated with any wheezing at 2 y of age (P for trend = 0.06 and 0.01 over quartiles of intake for vitamin E and zinc, respectively). Similar results were obtained for recurrent wheezing at 2 y of age with vitamin E (OR: 0.49; 95% CI: 0.27, 0.90) and zinc (OR: 0.49; 95% CI: 0.27, 0.87) (P for trend = 0.05 and 0.06 over quartiles of intake for vitamin E and zinc, respectively).

CONCLUSION

Our results suggest that higher maternal total intakes of antioxidants during pregnancy may decrease the risks for wheezing illnesses in early childhood.

Relations of glycemic index and glycemic load with plasma oxidative stress markers

BACKGROUND

Recent data suggest that acute hyperglycemia may increase in vivo free radical production. This increased production has been implicated in many disease processes.

OBJECTIVE

The objective was to investigate whether a diet with a high glycemic index (GI) or glycemic load (GL) is associated with greater oxidative stress as measured by 2 lipid peroxidation markers, malondialdehyde (MDA) and F2-isoprostanes (IsoPs).

DESIGN

Plasma MDA and IsoP concentrations were measured in 292 healthy adults, and dietary GI and GL were assessed by using a validated food-frequency questionnaire. Cross-sectional associations between GI, GL, and the 2 markers were examined by using multiple regression techniques with adjustment for potential confounding variables.

RESULTS

Dietary GI was positively associated with both plasma MDA and IsoPs. The mean multivariate-adjusted MDA concentrations increased from 0.55 to 0.73 micromol/L as GI increased from the lowest to the highest quartile (P for trend = 0.02); the corresponding IsoP concentrations increased from 0.034 to 0.040 ng/mL (P for trend = 0.03). GL was positively associated with both MDA and IsoPs, but the linear relation was significant only for MDA. In addition, a marginally significant interaction between overall GI and body mass index (BMI; in kg/m2) for plasma MDA was observed (P = 0.09). The positive association between overall GI and MDA was stronger in those with a BMI < 26.5 than for those with a BMI > or = 26.5.

CONCLUSIONS

Chronic consumption of high-GI foods may lead to chronically high oxidative stress. A low-GI diet, not a low-carbohydrate diet, appears to be beneficial in reducing oxidative stress.

Isoprostane-induced airway hyperresponsiveness is dependent on internal Ca2+ handling and Rho/ROCK signaling

We previously reported the ability of isoprostanes to induce airway hyperresponsiveness (AHR). In this study, we examined the signaling mechanisms underlying that phenomenon with the standard muscle bath technique. Responses to a threshold concentration of carbachol (CCh, 3 x 10(-9) M) were significantly augmented by pretreatment for 20 min with 8-isoprostaglandin E(2) (15-E(2t)-IsoP, 10(-6) M): this AHR was obliterated in tissues pretreated with the selective Rho kinase (ROCK) inhibitor Y-27632 added 20 min before isoprostane, but not by cyclopiazonic acid (CPA). Increasing the CCh concentration to 3 x 10(-8) M (still considerably less than the half-maximally effective concentration of CCh) evoked larger contractions that were also augmented significantly by 15-E(2t)-IsoP: this AHR was completely abolished in tissues pretreated with CPA as well as those pretreated with Y-27632. We noted, however, that Y-27632 and CPA profoundly effect baseline tone and the cholinergic response per se, which confounds the interpretation of the data summarized above. We therefore modified the protocol by using combinations of CCh and blocker (CPA, Y-27632, or nifedipine) that were equieffective. In this way, we found that AHR could not be demonstrated under conditions in which Rho/ROCK signaling or Ca(2+) release was abolished (by Y-27632 and CPA, respectively). Likewise, other autacoids that act through G protein-coupled receptors via Rho/ROCK and Ca(2+) release (serotonin, histamine) mimicked this effect of isoprostane, whereas bradykinin did not. We conclude that isoprostane-induced AHR is mediated in part through an action on Rho/ROCK signaling. This novel finding may contribute to a better understanding of the mechanisms underlying AHR and asthma.

Low maternal vitamin E intake during pregnancy is associated with asthma in 5-year-old children

RATIONALE

We have previously reported an association between reduced maternal vitamin E intake during pregnancy and wheezing in 2-yr-old children.

OBJECTIVES

To assess whether maternal nutrient intake during pregnancy is associated with asthma-related outcomes in children aged 5 yr.

METHODS

A longitudinal cohort study of 1,861 children born to women recruited during pregnancy and followed up at 5 yr.

MEASUREMENTS

Maternal nutrient status was assessed by a food frequency questionnaire and plasma levels. Respiratory and food frequency questionnaires were completed at 5 yr and children were invited for measurement of spirometry and skin-prick testing.

MAIN RESULTS

Symptom and food frequency questionnaire data were available for 1,253 and 1,120 children, respectively; 700 children were skin prick tested, and FEV(1) was measured in 478 and exhaled nitric oxide in 167 children. In 5-yr-old children, maternal vitamin E intake during pregnancy was negatively associated with wheeze in previous year (odds ratio per intake quintile, 0.82; 95% confidence interval, 0.71-0.95), asthma ever (0.84, 0.72-0.98), asthma and wheeze in previous year (0.79, 0.65-0.95), and persistent wheezing (0.77, 0.63-0.93). Maternal plasma alpha-tocopherol during pregnancy was positively associated with post-bronchodilator FEV(1) at 5 yr, with a 7-ml (95% confidence interval, 0-14; p = 0.04) increase in FEV(1) per microg/ml alpha-tocopherol. Maternal zinc intake during pregnancy was negatively associated with asthma ever (0.83, 0.71-0.78) and active asthma (0.72, 0.59-0.89). There were no associations between children's nutrient intake and respiratory outcomes.

CONCLUSION

Maternal intake of foods containing vitamin E and zinc during pregnancy is associated with differences in the risks of developing childhood wheeze and asthma.

Reactive oxidant species in asthma

PURPOSE OF REVIEW

This overview summarizes some recent studies on the balance of oxidants to antioxidants in patients with asthma. The aim of the review is to compare studies on the changes in oxidants/antioxidants in stable asthma or in acute exacerbation of asthma.

RECENT FINDINGS

Our review of the recent literature in this field seems to indicate conflicting findings. Increased release of reactive oxygen species such as superoxide anion and hydrogen peroxide has been reported in exhaled breath condensates and from circulating granulocytes, and from the bronchoalveolar lavage cells of patients with asthma. In asthma, bronchial obstruction is associated with an increased spontaneous and stimulus-induced production of oxygen free radicals. The primary defense against reactive oxygen species is endogenous antioxidants, which are found to be altered in asthma. A marked decrease in plasma antioxidant capacity occurs. Superoxide dismutase activity is higher in erythrocytes and serum of asthmatic than in normal subjects and is diminished in cells from lavage and brushing samples of patients with asthma. Higher level of erythrocyte catalase activity has only been found in Chinese asthmatic patients while decreased glutathione peroxidase activity has been well documented.

SUMMARY

Since there are considerable discrepancies in erythrocyte or plasma antioxidant enzyme activity in patients with asthma, the problem at this time is attempting to sort out these conflicting results and to find their roles in the pathogenesis of asthma. There is good evidence that antioxidant compounds may have a potential role in the treatment of asthma, especially of asthma exacerbation.

F2-isoprostanes as markers of oxidative stress in vivo: an overview

The isoprostanes are a unique series of prostaglandin-like compounds formed in vivo via a non-enzymatic mechanism involving the free radical-initiated peroxidation of arachidonic acid. This article summarizes selected aspects regarding current knowledge of these compounds and their value as markers of oxidative injury. Novel aspects related to the biochemistry of isoprostane formation are discussed and methods by which these compounds can be analysed and quantified are summarized. A considerable portion of this article examines the utility of F(2)-isoprostanes as markers of oxidant injury in vivo. Numerous studies carried out over the past decade have shown that these compounds are extremely accurate measures of lipid peroxidation and have illuminated the role of oxidant injury in a number of human diseases including atherosclerosis, Alzheimer's disease and pulmonary disorders.

Prostanoids as pharmacological targets in COPD and asthma

COPD (Chronic Obstructive Pulmonary Disease) and bronchial asthma are two severe lung diseases which represent a major problem of world public health. Leukotrienes and prostanoids play an important role in the pathogenesis of pulmonary diseases. Prostanoids: prostaglandins (PGs) and thromboxane A2 (TXA2), the cyclooxygenase metabolites of arachidonic acid are implicated in the inflammatory cascade that occurs in asthmatic airways. Recently, the roles played by isoprostanes or prostaglandin-like compounds nonenzymatically generated via peroxidation of membrane phospholipids by reactive oxygen species, in particular F2-isoprostanes, in pulmonary pathophysiology have been highlighted. This article aims to provide an overview of the role of prostanoids and isoprostanes in the pathogenesis of COPD and asthma and to discuss the pharmacological strategies developed in prevention and/or treatment of these pathologies.

Inflammatory mediators in exhaled breath, induced sputum and saliva

BACKGROUND AND OBJECTIVE

Airway inflammation is assessed to monitor progression, control and treatment of asthma. The collection of exhaled breath condensate (EBC) provides a non-invasive alternative to induced sputum samples for the monitoring of airway inflammation. Both samples can be confounded by salivary contamination. The aim of this study was to compare the levels of inflammatory mediators in samples of EBC, induced sputum and saliva samples from subjects with asthma.

METHOD

EBC, saliva and induced sputum samples were collected from subjects with asthma (n=10). Total protein, IL-8, 8-isoprostane and surfactant protein A (SPA) were assessed in each sample.

RESULTS

Total protein, IL-8, 8-isoprostane and SPA were detected in all sputum samples. Only total protein and SPA were consistently measured in EBC, with levels at least 100-fold lower than those measured in induced sputum. In saliva, total protein, SPA and 8-isoprostane were detected in all samples, with IL-8 detected in 60% of samples.

CONCLUSIONS

Induced sputum is a reliable technique that can be used to assess markers of airway inflammation. While EBC is a simple and inexpensive technique to collect lower airway secretions, the detection of inflammatory mediators is variable, and further work is required to validate this technique to assess inflammatory mediators.

Leukocyte oxidant and antioxidant status in asthmatic patients

BACKGROUND

Oxidative stress mediated by reactive oxygen species (ROS) is recognized to contribute significantly to the inflammatory process of bronchial asthma (BA). These species are released into the airway by activated inflammatory cells such as leukocytes. In this study, we aimed to determine whether the oxidant-antioxidant balance is changed in leukocytes of patients with BA.

METHODS

Thirty eight patients (21 male, 17 female) aged 22-68 years and controls of 32 subjects (18 male, 14 female) aged 20-63 years were included in the study. A total of 10 mL venous blood was drawn, leukocytes were separated and lipid peroxidation (LPO), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and vitamin C levels were determined in both patients and controls.

RESULTS

Leukocyte LPO and SOD activity in the patient group were higher than that of controls (p <0.001 and p <0.05, respectively). However, leukocyte GSH-Px and vitamin C levels in the patient group were lower than that of controls (p <0.01 and p <0.001, respectively).

CONCLUSIONS

The results suggest that there are alterations in a wide array of oxidants and antioxidants with balance shifting toward increased oxidative stress in BA.

Correlation of systemic superoxide dismutase deficiency to airflow obstruction in asthma

RATIONALE

Increased oxidative stress and decreased superoxide dismutase (SOD) activity in the asthmatic airway are correlated to airflow limitation and hyperreactivity. We hypothesized that asthmatic individuals with higher levels of oxidative stress may have greater loss of SOD activity, which would be reflected systemically in loss of circulating SOD activity and clinically by development of severe asthma and/or worsening airflow limitation.

METHODS

To investigate this, serum SOD activity and proteins, the glutathione peroxidase/glutathione antioxidant system, and oxidatively modified amino acids were measured in subjects with asthma and healthy control subjects.

RESULTS

SOD activity, but not Mn-SOD or Cu,Zn-SOD protein, was lower in asthmatic serum as compared with control, and activity loss was significantly related to airflow limitation. Further, serum SOD activity demonstrated an inverse correlation with circulating levels of 3-bromotyrosine, a posttranslational modification of proteins produced by the eosinophil peroxidase system of eosinophils. Exposure of purified Cu,Zn-SOD to physiologically relevant levels of eosinophil peroxidase-generated reactive brominating species, reactive nitrogen species, or tyrosyl radicals in vitro confirmed that eosinophil-derived oxidative pathways promote enzyme inactivation.

CONCLUSION

These findings are consistent with greater oxidant stress in asthma leading to greater inactivation of SOD, which likely amplifies inflammation and progressive airflow obstruction.

Induced Sputum 8-Isoprostane Concentrations in Inflammatory Airway Diseases

Induced sputum 8-iso-prostaglandin F(2alpha) (PGF(2alpha)) concentrations may be a useful marker of oxidative stress in airways disease. This study examines oxidative stress (measured by 8-iso-PGF(2alpha)) in airway disease according to disease type (asthma and bronchiectasis), disease activity (stable and acute asthma), and disease pattern (intermittent, mild, moderate, and severe persistent asthma). We compared subjects with stable asthma (n = 71) and bronchiectasis (n = 23) with healthy control subjects (n = 29). Another group of patients with asthma (n = 39) were assessed during and after acute exacerbation. Induced sputum 8-iso-PGF(2alpha) concentrations were validated and found to be elevated in subjects with stable asthma and bronchiectasis versus control subjects (median [interquartile range] 216 [103-389] and 698 [264-1,613] ng/L vs. 123 [41-290] ng/L, p < 0.001) and increased as clinical asthma pattern worsened (intermittent 115 [42-153], mild persistent 116 [89-229] ng/L, moderate persistent 183 [110-317] ng/L, severe persistent 387 [102-587] ng/L; p = 0.010). Sputum 8-iso-PGF(2alpha) concentrations were elevated during acute asthma and decreased with recovery (458 [227-950] ng/L vs. 214 [148-304] ng/L, p = 0.0002). We conclude that 8-iso-PGF(2alpha) is involved in the pathophysiology of inflammatory airway diseases, being related to disease type, pattern, and activity. Analysis of 8-iso-PGF(2alpha) concentrations in induced sputum provides a useful tool for monitoring oxidative stress and investigating strategies aimed at reducing oxidative stress in airways disease.

Increased anti-oxidant enzyme activity and biological oxidation in placentae of pregnancies complicated by maternal asthma

Our previous work has demonstrated that alterations in placental function are associated with changes in fetal development in pregnancies complicated by asthma. The pathophysiology of asthma in adults and children and intrauterine growth restriction during pregnancy are associated with oxidative stress. Based on this information, we examined whether placental anti-oxidant pathways and markers of biological oxidation were altered in pregnancies complicated by asthma. Anti-oxidant enzyme activities of superoxide dismutase, glutathione peroxidase and thioredoxin reductase, thioredoxin concentrations, lipid and protein oxidation levels were measured in placentae of pregnancies complicated by asthma and compared to uncomplicated, non-asthmatic pregnancies. Placental tissue homogenates of pregnancies complicated by asthma demonstrated significantly increased levels of lipid peroxidation (25.7+/-1.8 micromol/mg protein versus 12.1+/-1.6 micromol/mg protein, P=0.008) and protein carbonyl concentrations (414.6+/-51.4 units/mg protein versus 222.3+/-32.6 units/mg protein, P=0.0032) when compared to non-asthmatic controls. The activities of the anti-oxidant proteins superoxide dismutase (2.17+/-0.09 units/mg protein versus 1.67+/-0.09 units/mg protein, P=0.014) and thioredoxin reductase (54.0+/-6.9 units/mg protein versus 28.7+/-6.0 units/mg protein, P=0.009) were significantly increased in the presence of maternal asthma. Placental thioredoxin levels (102.9+/-5.3 ng/mg protein versus 92.9+/-8.6 ng/mg protein, P=0.37) and glutathione peroxidase activity (27.3+/-2.2 mmol/min/mg protein versus 28.3+/-2.2 mmol/min/mg, P=0.83) were not significantly different in pregnancies complicated by asthma and non-asthmatic pregnancies. There was no effect of fetal sex, asthma severity or treatment for asthma on these pathways. Maternal asthma during pregnancy is associated with increased placental enzymatic anti-oxidant capacity and also increased protein oxidation suggesting there is a compensatory increase in anti-oxidant activity in response to increased oxidative stress.

The pulmonary biology of isoprostanes

Isoprostanes were first recognized as convenient markers of oxidative stress, but their powerful effects on a variety of cell functions are now also being increasingly appreciated. This is particularly true of the lung, which is comprised of a wide variety of different cell types (smooth muscle, innervation, epithelium, lymphatics, etc.), all of which have been shown to respond to exogenously applied isoprostanes. In this review, we summarize these biological responses in the lung, and also consider the roles that isoprostanes might play in a range of pulmonary clinical disorders.

Zinc metabolism in airway epithelium and airway inflammation: basic mechanisms and clinical targets. A review

In addition to basic housekeeping roles in metalloenzymes and transcription factors, dietary zinc (Zn) is an important immunoregulatory agent, growth cofactor, and cytoprotectant with anti-oxidant, anti-apoptotic, and anti-inflammatory roles. These properties of Zn are of particular importance in maintaining homeostasis of epithelial tissues which are at the front line of defense. This review is about the role of Zn in airway epithelium (AE). The first part focuses on the cellular biology of Zn, and what is known about its distribution and function in AE. The second part of the review considers evidence for altered Zn metabolism in asthma and other chronic diseases of airway inflammation. Important issues arise from a potential therapeutic perspective as to the optimal ways to monitor circulating and epithelial Zn levels in patients and the most effective means of supplementing these levels.

Oxidative stress in the pathogenesis of asthma

Asthma affects 5% to 10% of the population of the United States. In asthmatics, oxidative stress occurs not only as a result of inflammation but also from environmental exposure to air pollution. The specific localization of antioxidants in the lung and the adaptive changes during asthma underscore the importance of oxidative stress, and therapeutic interventions that decrease exposure to environmental reactive oxygen species or augment endogenous antioxidant defenses might be beneficial as adjunctive therapies in asthmatic patients.

alpha-Lipoic acid inhibits airway inflammation and hyperresponsiveness in a mouse model of asthma

BACKGROUND

Oxidative stress may play an important role in the pathogenesis of bronchial asthma.

OBJECTIVE

We evaluated the therapeutic effect of alpha-lipoic acid, a nonenzymatic antioxidant, in a mouse model of asthma.

METHODS

BALB/c mice were immunized intraperitoneally with ovalbumin (OVA) on days 1 and 14 and challenged with inhaled OVA on days 28, 29, and 30. Mice were fed OVA-free standard mouse chow with 0%, 0.125%, 0.25%, 0.5%, and 1% (wt/wt) alpha-lipoic acid during the immunization and challenge periods. On day 31, mice were challenged with inhaled methacholine, and enhanced pause was measured as an index of airway hyperresponsiveness. Severity of airway inflammation was determined by means of differential cell count of bronchoalveolar lavage (BAL) fluid and by means of histopathologic lung analysis. Levels of OVA-specific IgE in serum, IL-4 and IL-5 in BAL fluid, and intracellular reactive oxygen species in alveolar macrophages and lymphocytes obtained from regional perihilar lymph nodes were measured. Nuclear factor kappaB DNA-binding activity in lung tissues was analyzed by means of electrophoretic gel mobility shift assay.

RESULTS

Compared with untreated asthmatic mice, mice treated with alpha-lipoic acid had significantly reduced airway hyperresponsiveness, a lower proportion of eosinophils among BAL cells, and significantly improved pathologic lesion scores of the lungs. alpha-Lipoic acid also significantly reduced serum OVA-specific IgE concentrations, IL-4 and IL-5 concentrations in BAL fluid, and intracellular reactive oxygen species and nuclear factor kappaB DNA-binding activity.

CONCLUSION

These results suggest that oxidative stress plays an important role in asthmatic airway inflammation and that alpha-lipoic acid may be useful as adjuvant therapy for bronchial asthma.

Isoprostanes: novel bioactive products of lipid peroxidation

Isoprostanes, are a novel group of prostaglandin-like compounds that are biosynthesised from esterified polyunsaturated fatty acid (PUFA) through a non-enzymatic free radical-catalysed reaction. Several of these compounds possess potent biological activity, as evidenced mainly through their pulmonary and renal vasoconstrictive effects, and have short half-lives. It has been shown that isoprostanes act as full or partial agonists through thromboxane receptors. Both human and experimental studies have indicated associations of isoprostanes and severe inflammatory conditions, ischemia-reperfusion, diabetes and atherosclerosis. Reports have shown that F2-isoprostanes are authentic biomarkers of lipid peroxidation and can be used as potential in vivo indicators of oxidant stress in various clinical conditions, as well as in evaluations of antioxidants or drugs for their free radical-scavenging properties. Higher levels of F2-isoprostanes have been found in the normal human pregnancy compared to non-pregnancy, but their physiological role has not been well studied so far. Since bioactive F2-isoprostanes are continuously formed in various tissues and large amounts of these potent compounds are found unmetabolised in their free acid form in the urine in normal basal conditions with a wide inter-individual variation, their role in the regulation of normal physiological functions could be of further biological interest, but has yet to be disclosed. Their potent biological activity has attracted great attention among scientists, since these compounds are found in humans and animals in both physiological and pathological conditions and can be used as reliable biomarkers of lipid peroxidation.

Glutathione and nitrite in induced sputum from patients with stable and acute asthma compared with controls

BACKGROUND

Oxidative stress is believed to play an important role in the pathogenesis of asthma. Determining the reduced glutathione (GSH) and nitric oxide (NO) contents of the airway is useful when investigating oxidative stress in the lung.

OBJECTIVE

To explore antioxidant defenses by measuring sputum GSH levels and to evaluate oxidant stress by measuring sputum nitrite (NO2-) levels in asthma patients.

METHODS

Sputum GSH, NO2-, cell counts, and plasma NO2- contents were evaluated in 11 patients with stable asthma, 10 patients with acute asthma attacks, and 11 controls.

RESULTS

The highest GSH content in sputum samples was in stable asthma patients compared with the other groups (P < .001), and patients with exacerbations of asthma had a greater GSH content than controls (P < .001). Mean sputum NO2- content was significantly lower in controls than in acute (P = .001) and stable (P < .001) asthma patients. There was no significant difference in sputum NO2- contents between acute and stable asthma patients, although there was a trend toward higher levels in acute asthma patients (P = .38).

CONCLUSIONS

Sputum induction can be used to obtain bronchial secretions for the evaluation of GSH and NO2- contents. Oxidative stress is chronic and probably less severe in patients with stable asthma. Glutathione and NO2- may serve as markers for determining the extent of the oxidative processes in asthma, which is characterized by chronic airway inflammation.

Stability of Measurements of Biomarkers of Oxidative Stress in Blood Over 36 Hours

Oxidative stress is hypothesized to play an important role in a variety of chronic diseases, but the short-term and long-term stability of measurements of biomarkers related to oxidative stress remains unclear. The objective of this study was to evaluate the stability of measurements of malondialdehyde (MDA), F2-isoprostanes, and fluorescent oxidation products in blood stored on ice within 36 hours until processing. Whole blood samples from six healthy women were processed at 0, 24, and 36 hours after being stored on ice. MDA was measured by the thiobarbituric acid–reactive substances assay with high-pressure liquid chromatography. F2-isoprostanes were measured by gas chromatography/mass spectrometry. The fluorescent oxidation products were measured by spectrofluorometry. Measurements of fluorescent oxidation products were very stable up to 36 hours. Intraclass correlation coefficients (ICC) were &gt;0.95 for each time interval (0 to 24 and 0 to 36 hours). Measurements of MDA were the least stable. The median increased significantly from 0 to 24 hours and from 0 to 36 hours. The ICC for MDA for each time interval (0 to 24 and 0 to 36 hours) was &lt;0.1. Finally, the median of F2-isoprostane measurements at each time point also increased significantly. ICCs were 0.45 for 0 to 24 hours and 0.09 for 0 to 36 hours. We conclude that measurements of fluorescent oxidation products in blood remain stable for up to 36 hours and may be used in large prospective epidemiologic studies of chronic diseases.

Augmentation of bovine airway smooth muscle responsiveness to carbachol, KCl, and histamine by the isoprostane 8-iso-PGE2

Isoprostanes are generated during periods of oxidative stress, which characterize diseases such as asthma and cystic fibrosis. They also elicit functional responses and may therefore contribute to the pathology of these diseases. We set out to examine the effects of isoprostanes on airway responsiveness to cholinergic stimulation. Muscle bath techniques were employed using isolated bovine tracheal smooth muscle. 8-Isoprostaglandin E2 (8-iso-PGE2) increased tone directly on its own, although the magnitude of this response, even at the highest concentration tested, was only a fraction of that evoked by KCl or carbachol. More importantly, though, pretreatment of the tissues with 8-iso-PGE2 (10 microM) markedly augmented responses to submaximal and even subthreshold concentrations of KCl, carbachol, or histamine, whereas maximal responses to these agents were unaffected by the isoprostane. The augmentative effect on cholinergic responsiveness was mimicked by PGE2 (0.1 microM) and by the FP agonists PGF2 (0.1 microM) and fluprostenol (0.1 microM), but not by the EP3 agonist sulprostone (0.1 microM) or the TP agonist U-46619 (0.1 microM). Antagonists of EP1 receptors (AH-6809 and SC-19920, 10 microM) and TP receptors (ICI-192605, 1 microM) had no effect on 8-iso-PGE2-induced augmentation of cholinergic responsiveness. We conclude that 8-iso-PGE2 induces nonspecific airway smooth muscle hyperresponsiveness through a non-TP non-EP prostanoid receptor.

The pulmonary biology of isoprostanes

Isoprostanes are widely recognized as useful markers of membrane lipid peroxidation. It seems to be less well appreciated, however, that they also elicit important biological responses, even though this was first shown at the same time that they were introduced as markers of oxidative stress. The past several years have seen the list of cells/tissues which are sensitive to isoprostanes grow considerably: in fact, as we summarize here, there is now evidence that essentially every cell type in the lung responds in some pathologically relevant way to isoprostanes. In this sense, they might well be considered as not just markers of oxidative stress and inflammation, but also as a novel group of inflammatory mediators. Moreover, in addition to their pathological effects, we summarize here the evidence which has led us to hypothesize that isoprostanes could play an important role in vascular smooth muscle physiology as "endothelium-derived hyperpolarizing factors."

Serum antioxidant concentrations among U.S. adults with self-reported asthma

Antioxidants may protect the lungs of people with asthma against oxidative stress. Among participants aged > or = 20 years from the Third National Health and Nutrition Examination Survey (1988-1994), we examined serum antioxidant concentrations of 771 persons with current asthma, 352 persons with former asthma, and 15,418 persons without asthma. After adjustment for age, participants with current asthma had similar mean concentrations of vitamin A, retinyl esters, vitamin C, vitamin E, vitamin E/cholesterol ratio, vitamin E/triglyceride ratio, alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein/zeaxanthin, lycopene, and selenium as participants without asthma. We repeated these analyses among participants who did not use vitamin or mineral supplements. After age adjustment, participants with current asthma had lower vitamin C and beta-cryptoxanthin concentrations and a lower mean vitamin E/triglyceride ratio than participants without asthma. In multiple linear regression models that included age, sex, race or ethnicity, education, smoking status, nonhigh-density lipoprotein cholesterol concentration, high-density lipoprotein cholesterol concentration, body mass index, physical activity, and alcohol use, asthma status was not significantly associated with any of the antioxidant concentrations. However, lower vitamin C concentrations were observed among people with current or former asthma than among people who never had asthma (p = 0.014). In the United States, people with asthma do not have manifest antioxidant deficiencies.

A solid dietary fat containing fish oil redistributes lipoprotein subclasses without increasing oxidative stress in men

There is a demand and need for healthy solid dietary fats. However, synthetic fats can be tailored to contain specific physiologic properties. Our goal was to design dietary solid test fats that would be both beneficial to the atherogenic lipid profile and stable against lipid peroxidation. Sixteen men (age 35-75 y) substituted 80 g of their normal dietary fat intake with test fat for two periods of 21 d each in a double-blind, randomized, crossover study. Although solid, both test fats were low in cholesterol-raising SFA. Test fat "F" contained 5 g/100 g long chain (n-3) fatty acids matched by oleic acid in test fat "O." Plasma total triacylglycerol (TAG), VLDL TAG, cholesterol in VLDL, and intermediate density lipoproteins (IDL) were lower (P < 0.05), whereas apolipoprotein (apo) B of the large LDL-2 (d = 1031-1042 g/L) subclass, and cholesterol of HDL(2b) subclass, were higher after intake of F than O fat (P < 0.05). There was no difference in the effect on in vivo oxidation measured as the ratio of plasma isoprostanes F(2) to arachidonic acid and urinary isoprostanes, whereas the vitamin E activity/plasma total lipids ratio was higher after intake of F than O (P = 0.008). In conclusion, a solid dietary fat containing (n-3) PUFA decreased plasma TAG, VLDL, and IDL cholesterol, and redistributed lipoprotein subclasses in LDL and HDL, with a higher concentration of the larger and less atherogenic subfractions. These changes took place without an increase in oxidative stress as measured by in vivo markers.

Localization of isoketal adducts in vivo using a single-chain antibody

Isoketals are highly reactive gamma-ketoaldehydes formed by the oxidation of arachidonic acid that rapidly adduct to proteins. To investigate the formation of isoketal adducts in vivo, we isolated and characterized a single-chain antibody from a phage displayed recombinant ScFv library that bound a model peptide adducted with synthetic 15-E2-isoketal. Recognition of isoketal adduct by this anti-isoketal adduct single-chain antibody was essentially independent of the amino acid sequence of adducted peptides or proteins. The antibody did not cross-react with 4-hydroxynonenal or 4-oxononanal adducts or with 15-F2t-isoprostane (8-iso-prostaglandin F2alpha). We investigated the formation of isoketal adducts in a well-established model of oxidative injury, hyperoxia. Exposure to >98% oxygen for 7 h dramatically increased both the number of immunoreactive airway epithelial cells and the intensity of immunoreactivity compared with animals exposed to normal room air (21% oxygen). We conclude that isoketal adducts form in epithelial cells as a result of high oxygen exposure and that this single-chain antibody provides a valuable tool to localize the formation of isoketal adducts in tissues in vivo.

Serum total antioxidant status in severe exacerbation of asthma: correlation with the severity of the disease

Oxidative processes, mediated by oxygen free radicals are recognized to contribute significantly to the inflammatory pathology of bronchial asthma. An imbalance between oxidants and antioxidants has also been proposed in this disease. This study examines the serum total antioxidant status (TAS) in asthmatic patients with severe exacerbation of their disease and the probable correlation with clinical or laboratory findings. The TAS was measured in 20 patients (10 men and 10 women, with a mean age of 41.95 +/- 20.75 years), using a colorimetric method. On the days of admission and discharge, the forced expiratory volume in 1 sec (FEV1), the partial arterial oxygen pressure (PaO2), and severity criteria were recorded and correlated with TAS at the same time. The TAS was also measured in 10 healthy subjects (8 men and 2 women, mean age of 39 +/- 9 years). A statistically significant decrease of TAS was observed on admission day compared to that on discharge day (0.98 +/- 0.08 vs. 1.12 +/- 0.17 mmol/L, p < 0.001, respectively, paired t-test) suggesting the presence of oxidative stress during an asthma attack. The TAS on admission was also statistically significantly decreased compared to that of normal subjects (0.98 +/- 0.08 vs. 1.19 +/- 0.09 mmo/L, p < 0.001, respectively, paired t-test). A statistically significant correlation was observed between FEV1 change and TAS change, from admission to discharge day (r = 0.58, p = 0.007, Pearson correlation). Finally, a statistically significant correlation was found between FEV1 change and TAS on discharge day (r = 0.65, p = 0.002). Decreased TAS was found during an asthma attack, probably as a consequence of increased oxidative stress. The TAS change was correlated with severity criteria, such as FEV1. Therefore, it seems that measurement of TAS could be a simple and useful tool in the evaluation of an asthma attack. The supplementary administration of antioxidants in future needs further clarification.

Exhaled breath condensate eicosanoids and sputum eosinophils in asthmatic children: a pilot study

Cysteinyl leukotrienes (cys-LTs), LTB4 and 8-isoprostane are increased in the exhaled breath condensate (EBC) from asthmatic patients. The aim of this study was to investigate whether the measurement of cys-LTs, LTB4 and 8-isoprostane in EBC can reflect the level of airway inflammation assessed by induced sputum in asthmatic children sensitized to house dust mite (HDM) during natural avoidance of HDM allergens. Twelve children were evaluated at the time of admission (T0) and after 3 months of stay (T1) at the Istituto Pio XII (Misurina, Italian Dolomites 1756 m). Sputum eosinophil percentage and measurement of cys-LTs, LTB4 and 8-isoprostanes in the breath condensate at T0 and T1 were evaluated. Eosinophil percentage in induced sputum was 8.5 +/- 1.1% at T0 and 3.5 +/- 0.4% at T1 (p = 0.011). Neutrophil percentage in sputum was 1.1 +/- 0.5% at T0 and 1.5 +/- 1.0% at T1 (ns). Cys-LTs mean level was 14.24 +/- 4.53 pg/ml at T0 and 4.65 +/- 0.68 pg/ml at T1 (p = 0.0125). LTB4 level was 2.36 +/- 0.19 pg/ml at T0 and 2.41 +/- 0.23 pg/ml at T1 (ns). 8-Isoprostane level reduced from 17.47 +/- 3.18 pg/ml at T0 to 7.36 +/- 3.26 pg/ml at T1 (p = 0.003). This study show that exhaled cys-LTs and 8-isoprostane, as well as eosinophil percentage in induced sputum, are reduced after allergen avoidance in asthmatic children suggesting a potential application of EBC for the non-invasive evaluation of airway inflammation in asthma in allergic asthmatic children.

Vasoconstrictor responses, and underlying mechanisms, to isoprostanes in human and porcine bronchial arterial smooth muscle

We investigated the effects of five different isoprostanes (8-iso PGE1, 8-iso PGE2, 8-iso PGF1alpha, 8-iso PGF2alpha and 8-iso PGF2beta) on vasomotor tone in human and porcine bronchial arterial tissues. In the human bronchial arteries, 8-iso PGE2 and 8-iso PGF2alpha evoked powerful constrictions (magnitudes several fold greater than the responses to high millimolar KCl) with negative log concentration causing 50% excitation (EC50) values of 6.8 and 6.5, respectively; 8-iso PGE1 was less potent (EC50 not calculated, since a clear peak contraction was not obtained), while the other isoprostanes were largely ineffective. In the porcine arteries, on the other hand, all three F-ring isoprostanes as well as 8-iso PGE2 evoked constrictor responses, although the peak magnitudes were approximately 50% of the KCl-evoked response; 8-iso PGE2 and 8-iso PGF2alpha were the most potent, with negative log EC50 values of 6.5. We next sought to characterize the signaling pathways underlying the vasoconstrictor responses to 8-iso PGE2, since this was the most potent of the isoprostanes we tested. These responses were largely reversed by the thromboxane A2-selective (TP) prostanoid receptor antagonist ICI 192605 (10-8 m; 4(Z)-6-[(2,4,5 cis)2-(2-chlorophenyl)-4-(2-hydroxy phenyl)1,3-dioxan-5-yl]hexenoic acid) as well as by the nonspecific tyrosine kinase inhibitor genistein (10-5 and 10-4 m), and were reversed approximately 50% by the Rho-kinase inhibitor Y27632 (10-5 m; (+)-(R)-trans-4-(1-aminoethyl)-N-(pyridyl) cyclohexanecarboxamide dihydrochloride). We conclude, therefore, that 8-iso PGE2 constricts bronchial vasculature through the activation of TP receptors, which in turn trigger tyrosine kinase and Rho-kinase activities, resulting in powerful vasoconstriction. These findings are highly relevant to lung transplantation and to exercise-induced asthma.

Peroxynitrite-induced oxidation of plasma lipids is enhanced in stable hemodialysis patients

BACKGROUND

The relationship between end-stage renal disease (ESRD), hemodialysis, and oxidative stress is controversial. To determine whether ESRD causes oxidative stress, we measured basal levels of plasma F2-isoprostanes as a marker of lipid peroxidation in vivo, and peroxynitrite-stimulated formation of F2-isoprostanes, as a marker of the oxidizibility of plasma lipids in vitro, before and after routine hemodialysis.

METHODS

Total plasma F2-isoprostanes were measured by gas chromatography-mass spectrometry (GC-MS) before and after the oxidation of plasma lipids with the peroxynitrite-generating compound, 3-morpholino-sydnonimine (SIN-1), in 23 patients with ESRD patients undergoing regular hemodialysis, and 14 controls. Plasma vitamin E concentrations were measured by high-performance liquid chromatography (HPLC).

RESULTS

There was no difference in basal plasma concentrations of F2-isoprostanes in the ESRD group prior to hemodialysis, 246 +/- 20 pg/mL, compared to controls, 252 +/- 28 pg/mL, or immediately on completion of hemodialysis, 236 +/- 14 pg/mL. Incubation of control plasma with SIN-1 caused the formation of F2-isoprostanes with plasma concentrations increasing to 987 +/- 54 pg/mL at 6 hours. The formation of F2-isoprostanes stimulated by SIN-1 was markedly enhanced in the plasma obtained from patients undergoing hemodialysis at 1861 +/- 174 pg/mL, P < 0.001, and SIN-1-induced formation of F2-isoprostanes was further increased in plasma obtained immediately after hemodialysis at 2437 +/- 168 pg/mL, P < 0.001. Incubation of plasma with SIN-1 resulted in the net consumption of vitamin E.

CONCLUSION

Although basal plasma F2-isoprostanes were similar in patients with ESRD compared with controls, the presence of oxidative stress in patients with ESRD was unmasked when the plasma was stressed by peroxynitrite generated from SIN-1, and this was enhanced further by hemodialysis.

Cysteinyl leukotrienes and 8-isoprostane in exhaled breath condensate of children with asthma exacerbations

BACKGROUND

Cysteinyl leukotrienes (Cys-LTs) and isoprostanes are inflammatory metabolites derived from arachidonic acid whose levels are increased in the airways of asthmatic patients. Isoprostanes are relatively stable and specific for lipid peroxidation, which makes them potentially reliable biomarkers for oxidative stress. A study was undertaken to evaluate the effect of a course of oral steroids on Cys-LT and 8-isoprostane levels in exhaled breath condensate of children with an asthma exacerbation.

METHODS

Exhaled breath condensate was collected and fractional exhaled nitric oxide (FE(NO)) and spirometric parameters were measured before and after a 5 day course of oral prednisone (1 mg/kg/day) in 15 asthmatic children with an asthma exacerbation. Cys-LT and 8-isoprostane concentrations were measured using an enzyme immunoassay. FE(NO) was measured using a chemiluminescence analyser. Exhaled breath condensate was also collected from 10 healthy children.

RESULTS

Before prednisone treatment both Cys-LT and 8-isoprostane concentrations were higher in asthmatic subjects (Cys-LTs, 12.7 pg/ml (IQR 5.4-15.6); 8-isoprostane, 12.0 pg/ml (9.4-29.5)) than in healthy children (Cys-LTs, 4.3 pg/ml (2.0-5.7), p=0.002; 8-isoprostane, 2.6 pg/ml (2.1-3.0), p<0.001). After prednisone treatment there was a significant decrease in both Cys-LT (5.2 pg/ml (3.9-8.8), p=0.005) and 8-isoprostane (8.4 pg/ml (5.4-11.6), p=0.04) concentrations, but 8-isoprostane levels remained higher than in controls (p<0.001). FE(NO) levels, which fell significantly after prednisone treatment (p<0.001), did not correlate significantly with either Cys-LT or 8-isoprostane concentrations.

CONCLUSION

After a 5 day course of oral prednisone there is a reduction in Cys-LT and 8-isoprostane levels in EBC of children with an asthma exacerbation, although 8-isoprostane levels remain higher than in controls. This finding suggests that corticosteroids may not be fully effective in reducing oxidative stress in children with an exacerbation of asthma.

Aldehydes and glutathione in exhaled breath condensate of children with asthma exacerbation

Oxidative stress is implicated in the pathogenesis of asthma, and clinical studies show an imbalance in the level of oxidants to the level of antioxidants in subjects with asthma. Aldehydes and glutathione are examples of biomarkers of oxidant-induced damage and antioxidant status in asthma, respectively. In the study, we applied analytical techniques based on liquid chromatography for the assessment of aldehydes and glutathione in the exhaled breath condensate of children with asthma and in control subjects without asthma. Twelve subjects with asthma were evaluated at exacerbation and after 5 days of therapy with prednisone. At exacerbation, malondialdehyde levels were higher in patients with asthma (30.2 +/- 2.4 nM) than in control subjects (19.4 +/- 1.9 nM, p = 0.002) and were reduced after steroid therapy (18.5 +/- 1.6 nM, p = 0.001). At exacerbation, glutathione levels were lower in subjects with asthma (5.96 +/- 0.6 nM) than in control subjects (14.1 +/- 0.8 nM, p < 0.0001) and were increased after the therapy (8.44 +/- 1.2 nM, p = 0.04). Malondialdehyde and glutathione both in subjects with asthma and control subjects were negatively correlated (r = -0.5, p = 0.001). The study shows that aldehydes and glutathione are detectable in the exhaled breath condensate of children with asthma and healthy children and that their levels are modified during asthma exacerbation and after a 5-day course of therapy with oral prednisone.

Increased oxidative stress and altered levels of antioxidants in asthma

BACKGROUND

Reactive oxygen species might play an important role in the modulation of airway inflammation. There is evidence of an oxidant-antioxidant imbalance in asthma. Although several oxidants and antioxidants are likely to be involved, alterations in only limited parameters have been studied in isolation.

OBJECTIVE

We investigated changes in a wide range of oxidants and antioxidants to create a comprehensive picture of oxidant-antioxidant imbalance.

METHODS

In the peripheral blood of 38 patients with bronchial asthma and 23 control subjects, oxidative stress was measured in terms of superoxide anion generation by leukocytes, lipid peroxidation products, total nitrates and nitrites, total protein carbonyls, and total protein sulfhydrils in plasma. Antioxidant status was evaluated by measuring red blood cell superoxide dismutase and catalase activity, total blood glutathione, and glutathione peroxidase activity in red blood cells and leukocytes and total antioxidant capacity in plasma.

RESULTS

Asthmatic patients showed increased superoxide generation from leukocytes, increased total nitrites and nitrates, increased protein carbonyls, and increased lipid peroxidation products and decreased protein sulfhydrils in plasma, indicating increased oxidative stress. They also showed increased superoxide dismutase activity in red blood cells and increased total blood glutathione and decreased glutathione peroxidase activity in red blood cells and leukocytes. Red blood cell catalase activity and the total antioxidant capacity of plasma were not altered.

CONCLUSION

There are alterations in a wide array of oxidants and antioxidants, with balance shifting toward increased oxidative stress in asthma. Therapeutic augmentation of the antioxidant defenses might be beneficial.

The isoprostanes: their role as an index of oxidant stress status in human pulmonary disease

The isoprostanes are a unique series of prostaglandin-like compounds formed in vivo from the free radical-initiated peroxidation of arachidonic acid independent of the cyclooxygenase enzyme. This article summarizes selected aspects regarding our current knowledge of these compounds and what are considered avenues for future research. Novel aspects related to the biochemistry of isoprostane formation are discussed first, followed by a summary of methods by which these compounds are analyzed. A considerable portion of this article deals with the utility of measuring isoprostanes as markers of oxidant injury in vitro and in vivo, particularly in pulmonary diseases. Studies performed over the past decade have shown that these compounds are extremely accurate measures of lipid peroxidation in animals and humans and have illuminated the role of oxidant injury in a number of human diseases, including those related to the lung.

Dose-dependent onset and cessation of action of inhaled budesonide on exhaled nitric oxide and symptoms in mild asthma

BACKGROUND

Dose dependent anti-inflammatory effects of inhaled corticosteroids in asthma are difficult to demonstrate in clinical practice. The anti-inflammatory effect of low dose inhaled budesonide on non-invasive exhaled markers of inflammation and oxidative stress were assessed in patients with mild asthma.

METHODS

28 patients entered a double blind, placebo controlled, parallel group study and were randomly given either 100 or 400 micro g budesonide or placebo once daily, inhaled from a dry powder inhaler (Turbohaler), for 3 weeks followed by 1 week without treatment. Exhaled nitric oxide (NO), exhaled carbon monoxide (CO), nitrite/nitrate, S-nitrosothiols, and 8-isoprostanes in exhaled breath condensate were measured four times during weeks 1 and 4, and once a week during weeks 2 and 3.

RESULTS

A dose-dependent speed of onset and cessation of action of budesonide was seen on exhaled NO and asthma symptoms. Treatment with 400 micro g/day reduced exhaled NO faster (-2.06 (0.37) ppb/day) than 100 micro g/day (-0.51 (0.35) ppb/day; p<0.01). The mean difference between the effect of 100 and 400 micro g budesonide was -1.55 ppb/day (95% CI -2.50 to -0.60). Pretreatment NO levels were positively related to the subsequent speed of reduction during the first 3-5 days of treatment. Faster recovery of exhaled NO was seen after stopping treatment with budesonide 400 micro g/day (1.89 (1.43) ppb/day) than 100 micro g/day (0.49 (0.34) ppb/day, p<0.01). The mean difference between the effect of 100 and 400 micro g budesonide was 1.40 ppb/day (95% CI -0.49 to 2.31). Symptom improvement was dose-dependent, although symptoms returned faster in patients treated with 400 micro g/day. A significant reduction in exhaled nitrite/nitrate and S-nitrosothiols after budesonide treatment was not dose-dependent. There were no significant changes in exhaled CO or 8-isoprostanes in breath condensate.

CONCLUSION

Measurement of exhaled NO levels can indicate a dose-dependent onset and cessation of anti-inflammatory action of inhaled corticosteroids in patients with mild asthma.

Antioxidant supplementation and lung functions among children with asthma exposed to high levels of air pollutants

To evaluate whether acute effects of ozone, nitrogen dioxide, and particulates with mass median diameter less than 10 micro m could be attenuated by antioxidant vitamin supplementation, we conducted a randomized trial using a double-blinded design. Children with asthma (n = 158) who were residents of Mexico City were randomly given a daily supplement of vitamins (50 mg/day of vitamin E and 250 mg/day of vitamin C) or a placebo and were followed from October 1998 to April 2000. Pulmonary function tests were carried out twice a week in the morning. During the follow-up observation period, the mean 1-hour maximum ozone level was 102 ppb (SD = 47), and the mean 24-hour average PM(10) level was 56.7 micro g/m(3) (SD = 27.4). In children with moderate and severe asthma, ozone levels 1 day before spirometry were inversely associated significantly with forced expiratory flow (FEF(25-75)) (-13.32 ml/second/10 ppb; p = 0.000), FEV(1) (-4.59 ml/10 ppb; p = 0.036), and peak expiratory flow (PEF) (-15.01 ml/second/10 ppb; p = 0.04) in the placebo group after adjusting for potential confounding factors. No association between ozone and lung functions was observed in the supplement group. We observed significant differences in lung function decrements between groups for FEF(25-75) and PEF. Our results suggest that supplementation with antioxidants might modulate the impact of ozone exposure on the small airways of children with moderate to severe asthma.