Increased oxidative stress in acute exacerbations of asthma

Nasal oxidative stress mediating the effects of colder temperature exposure on pediatric asthma symptoms

BACKGROUND

Colder temperature exposure is a known trigger for pediatric asthma exacerbation. The induction of oxidative stress is a known pathophysiologic pathway for asthma exacerbation. However, the role of oxidative stress in linking colder temperature exposure and worsened pediatric asthma symptoms is poorly understood.

METHODS

In a panel study involving 43 children with asthma, aged 5-13 years old, each child was visited 4 times with a 2-week interval. At each visit, nasal fluid, urine, and saliva samples were obtained and measured for biomarkers of oxidative stress in the nasal cavity (nasal malondialdehyde [MDA]), the circulatory system (urinary MDA), and the oral cavity (salivary MDA). Childhood Asthma-Control Test (CACT) was used to assess asthma symptoms.

RESULTS

When ambient daily-average temperature ranged from 7 to 18 °C, a 2 °C decrement in personal temperature exposures were significantly associated with higher nasal MDA and urinary MDA concentrations by 47-77% and 6-14%, respectively. We estimated that, of the decrease in child-reported CACT scores (indicating worsened asthma symptoms and asthma control) associated with colder temperature exposure, 14-57% were mediated by nasal MDA.

CONCLUSION

These results suggest a plausible pathway that colder temperature exposure worsens pediatric asthma symptoms partly via inducing nasal oxidative stress.

IMPACT

The role of oxidative stress in linking colder temperature exposure and worsened asthma symptoms is still poorly understood. Lower temperature exposure in a colder season was associated with higher nasal and systemic oxidative stress in children with asthma. Nasal MDA, a biomarker of nasal oxidative stress, mediated the associations between colder temperature exposures and pediatric asthma symptoms. The results firstly suggest a plausible pathway that colder temperature exposure worsens pediatric asthma symptoms partly via inducing oxidative stress in the nasal cavity.

Does Oxidative Stress Along with Dysbiosis Participate in the Pathogenesis of Asthma in the Obese?

The most important environmental factor that can play a key role in the development of asthma in the obese is overproduction of reactive oxygen species (ROS). The aim of the study was to examine changes in the concentration of oxidative stress parameters in the lungs, bronchoalveolar lavage (BAL) fluid and blood of mice in models of asthma or/and obesity caused by high-fat diet (HFD). The concentrations of 4-HNE and isoprostanes in the lungs of the animals were measured. BAL fluid levels of hydrogen peroxide were marked. Additionally, thiobarbituric acid reactive substances (TBARS) and ferric reducing ability of plasma (FRAP) were used as biomarkers of oxidative stress in the blood. Administration of lipoic acid (LA), a probiotic with standard-fat diet (SFD, 10% fat) and low-fat diet (LFD, 5% fat) significantly decreased the concentration of 4-HNE as compared to the OVA (ovalbumin) + HFD group (p < 0.05). Treatment with low-fat diet or LFD in combination with apocynin insignificantly decreased H₂O₂ values as compared to the OVA + HFD group. Supplementation of probiotic with SFD and LFD significantly decreased the concentration of TBARS as compared to the OVA + SFD and saline + HDF groups (p < 0.05). Significantly lower concentrations of TBARS were also observed in the LA plus LFD group (p < 0.05) as compared to the OVA + HFD group. Low-fat diet with probiotic significantly increased the concentration of FRAP as compared to the obese mice (p = 0.017). Treatment with LFD in combination with LA significantly increased FRAP values as compared to the obese and obese asthmatic mice (p < 0.001).

Oral cavity response to air pollutant exposure and association with pulmonary inflammation and symptoms in asthmatic children

Exposure to fine particulate matter (PM_2.5) and ozone (O₃) may lead to inflammation and oxidative damage in the oral cavity, which is hypothesized to contribute to the worsening of airway inflammation and asthma symptoms. In this panel study of 43 asthmatic children aged 5-13 years old, each child had 4 clinic visits with a 2-week interval between two consecutive visits. At each visit, saliva samples were collected and subsequently analyzed for interleukin 6 (IL-6) and eosinophil cationic protein (ECP) as biomarkers of inflammation and malondialdehyde (MDA) as a biomarker of oxidative stress in the oral cavity. At each visit, children were measured for fractional exhaled nitric oxide (FeNO) as a marker of pulmonary inflammation. Asthma symptoms of these children were measured using the Childhood Asthma Control Test (C-ACT). We found that an interquartile range (IQR) increase in 24-h average personal exposure to PM_2.5 measured 1 and 2 days prior was associated with increased salivary IL-6 concentration by 3.0% (95%CI: 0.2%-6.0%) and 4.2% (0.7%-8.0%), respectively. However, we did not find a clear association between personal O₃ exposure and any of the salivary biomarkers, except for a negative association between salivary MDA and O₃ exposure measured 1 day prior. An IQR increase in salivary IL-6 concentration was associated with significantly increased FeNO by 28.8% (4.3%-53.4%). In addition, we found that increasing salivary IL-6 concentrations were associated with decreased individual and total C-ACT scores, indicating the worsening of asthma symptoms. We estimated that 13.2%-22.2% of the associations of PM_2.5 exposure measured 1 day prior with FeNO and C-ACT scores were mediated by salivary IL-6. These findings suggest that the induction of inflammation in the oral cavity may have played a role in linking air pollution exposure with the worsening of airway inflammation and asthma symptoms.

Exacerbation of allergic asthma by somatic antigen of Echinococcus granulosus in allergic airway inflammation in BALB/c mice

BACKGROUND

There is ample evidence demonstrating a reverse relationship between helminth infection and immune-mediated diseases. Accordingly, several studies have shown that Echinococcus granulosus infection and hydatid cyst compounds are able to suppress immune responses in allergic airway inflammation. Previous studies have documented the ability of hydatid cysts to suppress aberrant Th2 immune response in a mouse model of allergic asthma. However, there is a paucity of research on the effects of protoscoleces on allergic asthma. Thus, this study was designed to evaluate the effects of somatic antigens of protoscoleces in a murine model of allergic airway inflammation.

METHODS

Ovalbumin (OVA)/aluminum hydroxide (alum) was injected intraperitoneally to sensitize BALB/c mice over a period of 0 to 7 days, followed by challenge with 1% OVA. The treatment group received somatic antigens of protoscoleces emulsified with PBS on these days in each sensitization before being challenged with 1% OVA on days 14, 15, and 16. The effects of somatic antigens of protoscoleces on allergic airway inflammation were evaluated by examining histopathological changes, the recruitment of inflammatory cells in the bronchoalveolar lavage, cytokine production in the homogenized lung tissue (IL-4, IL-5, IL-10, IL-17, and IFN-γ), and total antioxidant capacity in serum.

RESULTS

Overall, administration of somatic antigens of protoscoleces exacerbated allergic airway inflammation via increased Th2 cytokine levels in the lung homogenate, recruitment of eosinophils into bronchoalveolar lavage fluid, and pathological changes. In addition, total antioxidant capacity and IFN-γ levels declined following the administration of somatic antigens.

CONCLUSIONS

The results revealed that the co-administration of somatic products of protoscoleces with OVA/alum contributed to the exacerbation of allergic airway inflammation in BALB/c mice. Currently, the main cause of allergic-type inflammation exacerbation is unknown, and further research is needed to understand the mechanism of these interactions.

Exercise Training Induces a Shift in Extracellular Redox Status with Alterations in the Pulmonary and Systemic Redox Landscape in Asthma

Redox dysregulation and oxidative stress have been implicated in asthma pathogenesis. Exercise interventions improve symptoms and reduce inflammation in asthma patients, but the underlying mechanisms remain unclear. We hypothesized that a personalised exercise intervention would improve asthma control by reducing lung inflammation through modulation of local and systemic reactive species interactions, thereby increasing antioxidant capacity. We combined deep redox metabolomic profiling with clinical assessment in an exploratory cohort of six female patients with symptomatic asthma and studied their responses to a metabolically targeted exercise intervention over 12 weeks. Plasma antioxidant capacity and circulating nitrite levels increased following the intervention (p = 0.028) and lowered the ratio of reduced to oxidised glutathione (p = 0.029); this was accompanied by improvements in physical fitness (p = 0.046), symptoms scores (p = 0.020), quality of life (p = 0.046), lung function (p = 0.028), airway hyperreactivity (p = 0.043), and eosinophilic inflammation (p = 0.007). Increased physical fitness correlated with improved plasma antioxidant capacity (p = 0.019), peak oxygen uptake and nitrite changes (p = 0.005), the latter also associated with reductions in peripheral blood eosinophil counts (p = 0.038). Thus, increases in “redox resilience” may underpin the clinical benefits of exercise in asthma. An improved understanding of exercise-induced alterations in redox regulation offers opportunities for greater treatment personalisation and identification of new treatment targets.

Malondialdehyde in Nasal Fluid: A Biomarker for Monitoring Asthma Control in Relation to Air Pollution Exposure

Fine particulate matter (PM_2.5) and ozone (O₃) may exert oxidative damage in the nose, which is hypothesized to be associated with worsened asthma symptoms. This study, hence, is to explore whether an oxidative stress biomarker, malondialdehyde (MDA) in the nasal fluid, has the potential to aid personalized asthma control. In a panel study of 43 asthmatic children, 5-13 years old, each child was measured 4 times with a 2-week interval between consecutive clinic visits. At each visit, nasal fluid and urine samples were collected, and fractional exhaled nitric oxide (FeNO) was measured as a biomarker of pulmonary inflammation. In addition to nasal MDA, urinary MDA and 8-hydroxy-2'-deoxyguanosine (8-OHdG) were measured as biomarkers of systemic oxidative stress. We also assessed asthma symptoms using the Childhood Asthma-Control Test (C-ACT). We found that interquartile range (IQR) increases in 24 h average personal PM_2.5 exposure (22.2-33.5 μg/m³), estimated 0 to 5 days prior to a clinic visit, were associated with increased nasal MDA concentrations by 38.6-54.9%. Similarly, IQR increases in 24 h average personal O₃ exposure (7.7-8.2 ppb) estimated 2 to 4 days prior were associated with increased nasal MDA by 22.1-69.4%. Only increased PM_2.5 exposure was associated with increased FeNO. Increased nasal MDA concentration was associated with decreased total and individual C-ACT scores, indicating worsening of asthma symptoms. However, no significant associations were observed between urinary MDA or 8-OHdG and C-ACT scores. The results confirm that oxidative stress plays an important role in linking air pollution exposure and adverse respiratory health effects. These findings support that MDA in the nasal fluid may serve as a useful biomarker for monitoring asthma status, especially in relation to PM_2.5 and O₃ exposures, two known risk factors of asthma exacerbation.

Usefulness of routine blood test-driven clusters for predicting acute exacerbation in patients with asthma

AIM

Acute exacerbation (AE) is a significant burden in the management of asthma. In this study we aimed to investigate whether routine blood test results predicted AE in asthmatics.

METHODS

We applied k-means cluster to routine blood test results which included eosinophil counts, total calcium, phosphorus, uric acid (UA), total cholesterol, total protein, albumin, total bilirubin, alkaline phosphatase, aspartate transaminase (AST), alanine transferase (ALT), gamma-glutamyltransferase, blood urea nitrogen, creatinine, and high-sensitive C-reactive protein (hsCRP) obtained from 590 asthmatics. AEs collected over the prospective follow-up of one-year were used to evaluate clinical trajectories of these clusters.

RESULTS

Three blood clusters were identified. The essential features of each cluster can be characterized as follows: (i) high eosinophil count, UA, total cholesterol, AST, ALT, and hsCRP levels (Cluster 1); (ii) intermediate features (Cluster 2); (iii) low UA, total cholesterol and total bilirubin levels (Cluster 3). Kaplan-Meier analysis confirmed that clusters were strongly predictive of time to the first AE (log-rank P = 0.001). Hazard ratio for each group was as follows: Cluster 2 = 1, Cluster 1 = 2.67 (1 vs. 2, P = 4.68 × 10^-4), and Cluster 3 = 1.69 (2 vs. 3, P = 0.021).

CONCLUSIONS

We defined three blood clusters in asthmatics. These blood clusters are easily identifiable from routine test results and may help clinicians to predict the future risk of AE in asthmatics.

Genetic Signatures of Acute Asthma Exacerbation Related With Ineffective Response to Corticosteroid

Purpose

Acute exacerbation (AE) is an important domain of asthma management and may be related with ineffective response to corticosteroid. This study aimed to find mechanisms of AE using genome-wide gene expression profiles of blood cells from asthmatics and its perturbation by in vitro dexamethasone (Dex)-treatment.

Methods

We utilized lymphoblastoid B cells from 107 childhood asthmatics and peripheral blood mononuclear cells from 29 adult asthmatics who were treated with inhaled corticosteroids. We searched for a preserved co-expression gene module significantly associated with the AE rate in both cohorts and measured expression changes of genes belong to this module after Dex-treatment.

Results

We identified a preserved module composed of 77 genes. Among them, expressions of 2 genes (EIF2AK2 and NOL11) decreased significantly after Dex-treatment in both cohorts. EIF2AK2, a key gene acting antiviral defense mechanism, showed significantly higher expressions in asthmatics with AE. The protein repair pathway was enriched significantly in 64 genes which belong to the preserved module but showed no expression differences after Dex-treatment in both cohorts. Among them, MSRA and MSRB2 may play key roles by controlling oxidative stress.

Conclusions

Many genes belong to the AE rate-associated and preserved module identified in blood cells from childhood and adults asthmatics showed no expression changes after in vitro Dex-treatment. These findings suggest that we may need alternative treatment options to corticosteroids to prevent AE. EIF2AK2, MSRA and MSRB2 expressions on blood cells may help us select AE-susceptible asthmatics and adjust treatments to prevent AE.

Oxidative Stress Attenuates TLR3 Responsiveness and Impairs Anti-viral Mechanisms in Bronchial Epithelial Cells From COPD and Asthma Patients

COPD and asthma exacerbations are commonly triggered by rhinovirus infection. Potentially promoting exacerbations, impaired anti-viral signaling and attenuated viral clearance have been observed in diseased bronchial epithelium. Oxidative stress is a feature of inflammation in asthma and COPD and is prominent during exacerbations. It is not known whether oxidative stress affects the anti-viral signaling capacity. Bronchial epithelial cells from asthmatic and COPD donors were infected with rhinovirus or treated with the oxidative stressor H₂O₂ followed by exposure to the synthetic viral replication intermediate poly(I:C). Poly(I:C) was used to ascertain a constant infection-like burden. Gene and protein levels of antioxidants as well as anti-viral responses were measured 3 and 24 h post poly(I:C) exposure. Rhinovirus infection and poly(I:C) stimulation induced protein levels of the antioxidants SOD1 and SOD2. In asthmatic bronchial epithelial cells pre-treatment with H₂O₂ dose-dependently decreased the antioxidant response to poly(I:C), suggesting exaggerated oxidative stress. Further, poly(I:C)-induced IFNβ gene expression was reduced after pre-treatment with H₂O₂. This epithelial effect was associated with a reduced expression of the pattern recognition receptors RIG-I, MDA5 and TLR3 both on gene and protein level. Pre-treatment with H₂O₂ did not alter antioxidant responses in COPD bronchial epithelial cells and, more modestly than in asthma, reduced poly(I:C)-induced IFNβ gene expression. Knockdown of TLR3 but not RIG-I/MDA5 abrogated impairment of poly(I:C)-induced IFNβ gene expression by H₂O₂. We developed a method by which we could demonstrate that oxidative stress impairs anti-viral signaling in bronchial epithelial cells from asthmatic and COPD patients, most pronounced in asthma. The impairment apparently reflects reduced responsiveness of TLR3. These present findings shed light on molecular mechanisms potentially causing reduced interferon responses to rhinovirus infection at exacerbations in asthma and COPD. Together, our findings suggest a possible self-perpetuating vicious cycle underlying recurrent exacerbations, leading to an impaired anti-viral response, which in turn leads to viral-induced exacerbations, causing more airway inflammation.

Increasing complexity and interactions of oxidative stress in chronic respiratory diseases: An emerging need for novel drug delivery systems

Oxidative stress is intensely involved in enhancing the severity of various chronic respiratory diseases (CRDs) including asthma, chronic obstructive pulmonary disease (COPD), infections and lung cancer. Even though there are various existing anti-inflammatory therapies, which are not enough to control the inflammation caused due to various contributing factors such as anti-inflammatory genes and antioxidant enzymes. This leads to an urgent need of novel drug delivery systems to combat the oxidative stress. This review gives a brief insight into the biological factors involved in causing oxidative stress, one of the emerging hallmark feature in CRDs and particularly, highlighting recent trends in various novel drug delivery carriers including microparticles, microemulsions, microspheres, nanoparticles, liposomes, dendrimers, solid lipid nanocarriers etc which can help in combating the oxidative stress in CRDs and ultimately reducing the disease burden and improving the quality of life with CRDs patients. These carriers improve the pharmacokinetics and bioavailability to the target site. However, there is an urgent need for translational studies to validate the drug delivery carriers for clinical administration in the pulmonary clinic.

Oxidative stress and macrophages: driving forces behind exacerbations of asthma and chronic obstructive pulmonary disease?

Oxidative stress is a common feature of obstructive airway diseases like asthma and chronic obstructive pulmonary disease (COPD). Lung macrophages are key innate immune cells that can generate oxidants and are known to display aberrant polarization patterns and defective phagocytic responses in these diseases. Whether these characteristics are linked in one way or another and whether they contribute to the onset and severity of exacerbations in asthma and COPD remain poorly understood. Insight into oxidative stress, macrophages, and their interactions may be important in fully understanding acute worsening of lung disease. This review therefore highlights the current state of the art regarding the role of oxidative stress and macrophages in exacerbations of asthma and COPD. It shows that oxidative stress can attenuate macrophage function, which may result in impaired responses toward exacerbating triggers and may contribute to exaggerated inflammation in the airways.

The effect of erdosteine on airway defence mechanisms and inflammatory cytokines in the settings of allergic inflammation

INTRODUCTION

Mucoactive agent, erdosteine, besides mucolytic activity, is characterized by many other pharmacodynamic properties which could be beneficial in the management of inflammatory conditions.

BACKGROUND

Using guinea pig experimental model of allergic inflammation, we evaluated the ability of erdosteine to modulate airway defence mechanisms and inflammation after 10 days (10 mg/kg/day) administration.

METHODS

In vivo changes in specific airway resistance and amplitude of tracheal contraction were estimated to evaluate the bronchodilatory effect. The sensitivity of chemically induced cough reflex was estimated via in vivo method. The ciliary beat frequency assessed on brushed tracheal cells was used as an indicator of the mucociliary clearance rate. The concentrations of the inflammatory cytokines IL-4, IL-5, IL-13 and IL-10 were measured in BALF using multiplex detecting method.

RESULTS

Our data show that 10 days erdosteine administration resulted in bronchodilation and stimulation of ciliary beat frequency. Erdosteine did not affect the parameters of chemically induced cough reflex. Erdosteine demonstrated the modest decline in inflammatory cytokines IL-5, IL-13 and an increase in the concentration of IL-10, which is a potent regulator of inflammatory responses and plays a critical role in controlling allergic airway inflammation.

CONCLUSION

In summary, we can state, that erdosteine is multi-action drug and it seems to have many beneficial and complementary effect in the management of chronic inflammatory airway diseases complicated by viscous mucus.

Variants in genes coding for glutathione S-transferases and asthma outcomes in children

Our hypothesis was that children with mutations in genes coding for glutathione S-transferases (GST) have worse asthma outcomes compared with children with active type genotype. Data were collected in five populations. The rs1695 single nucleotide polymorphism (GSTP1) was determined in all cohorts (3692 children) and GSTM1 and GSTT1 null genotype were determined in three cohorts (2362 children). GSTT1 null (but not other genotypes) was associated with a minor increased risk for asthma attack and there were no significant associations between GST genotypes and asthma severity. Interactions between GST genotypes and SHS exposure or asthma severity with the study outcomes were nonsignificant. We find no convincing evidence that the GST genotypes studied are related to asthma outcomes.

Plasma total thiol pool in children with asthma: Modulation during montelukast monotherapy

BACKGROUND

Inflammation, which is a hallmark of asthma, is one of the main sources of oxidative stress in the human body. Thiols are powerful antioxidants that protect cells against the consequences of oxidative stress. We aimed to investigate whether asthma and montelukast monotherapy affect the total plasma thiol pool in children.

METHODS

A total of 60 children with asthma and 35 healthy controls participated in the study. Group I consisted of newly diagnosed asthmatics who did not have regular anti-asthmatic therapy previously. Group II consisted of patients who had been undertaking montelukast monotherapy regularly for at least 4 months. Plasma total antioxidant status (TAS) and plasma total thiol (PTT) were measured using spectrophotometric methods.

RESULTS

Bronchial asthma patients in both groups I and II had decreased median TAS levels compared with the control group (1.59 [interquartile range, 1.04-1.70] and 1.67 [1.50-1.75] vs. 2.98 [2.76-3.16] Trolox equiv./L, respectively; P<0.001). Group I had decreased PTT concentrations compared with the control group (0.18 [0.16-0.20] vs. 0.21 [0.19-0.22] mmol/L; P<0.001), and group II had similar PTT levels to the control group (0.20 [0.17-0.22] mmol/L; P>0.05). In addition, the median TAS and PTT levels for groups I and II were not statistically different (P>0.05). There was a positive correlation between TAS and PTT levels (rho=0.38, P<0.05) in group I.

CONCLUSION

In order to balance the oxidative stress, both TAS and PTT which are markers of the antioxidant system are reduced in children with asthma. Montelukast monotherapy can limit oxidative stress and thus restore PTT levels but not TAS levels in asthmatic children.

Effect of montelukast monotherapy on oxidative stress parameters and DNA damage in children with asthma

BACKGROUND

There is ample knowledge reported in the literature about the role of oxidative stress in asthma pathogenesis. It is also known that the interaction of reactive oxygen species with DNA may result in DNA strand breaks. The aim of this study was to investigate if montelukast monotherapy affects oxidative stress and DNA damage parameters in a population of pediatric asthma patients.

METHODS

Group I consisted of 31 newly diagnosed asthmatic patients not taking any medication, and group II consisted of 32 patients who had been treated with montelukast for at least 6 months. Forty healthy control subjects were also enrolled in the study. Plasma total oxidant status (TOS) and total antioxidant status (TAS) were measured to assess oxidative stress. DNA damage was assessed by means of alkaline comet assay.

RESULTS

The patients in both group I and group II had statistically significant higher plasma TOS (13.1 ± 4 and 11.1 ± 4.1 μmol H2O2 equivalent/liter, respectively) and low TAS levels (1.4 ± 0.5 and 1.5 ± 0.5 mmol Trolox equivalent/liter, respectively) compared with the control group (TOS: 6.3 ± 3.5 μmol H2O2 equivalent/liter and TAS: 2.7 ± 0.6 mmol Trolox equivalent/liter; p < 0.05). DNA damage was 18.2 ± 1.0 arbitrary units (a.u.) in group I, 16.7 ± 8.2 a.u. in group II and 13.7 ± 3.4 a.u. in the control group. There were statistically significant differences only between group I and the control group (p < 0.05).

CONCLUSIONS

According to the findings, montelukast therapy makes only minimal but not statistically significant improvement in all TOS, TAS and DNA damage parameters.

The association of asthma and atrial fibrillation--a nationwide population-based nested case-control study

BACKGROUND

Asthma and atrial fibrillation (AF) have been reported to be related to an increased risk of cardiovascular events. However, the relationship between asthma and AF has not been fully elucidated. The purpose of this study was to examine the association between asthma and AF risk.

METHODS

We conducted a population-based nested case-control study including a total of 7439 newly-diagnosed adult patients with AF and 10,075 age-, gender-, comorbidity-, and cohort entry date-matched subjects without AF from the Taiwan National Health Insurance database. Exposure to asthma as well as medications including bronchodilators and corticosteroid before the index date was evaluated to investigate the association between AF and asthma as well as concurrent medications.

RESULTS

AF patients were 1.2 times (adjusted OR 1.2, 95% CI 1.109-1.298) more likely to be associated with a future occurrence of asthma independent of comorbidities and treatment with corticosteroids and bronchodilator. In addition, the risks of new-onset AF were significantly higher among current users of inhaled corticosteroid, oral corticosteroids, and bronchodilators. Newly users (within 6 months) have the highest risk (inhaled corticosteroid: OR, 2.13; 95% CI, 1.226-3.701, P=0.007; oral corticosteroid: OR, 1.932; 95% CI, 1.66-2.25, P<0.001; non-steroid bronchodilator: OR, 2.849; 95% CI, 2.48-3.273, P<0.001). A graded association with AF risk was also observed among subjects treated with corticosteroid (inhaled and systemic administration) and bronchodilators. New users (within 6 months) of these medications had the highest risk of AF (ICS: OR, 2.13; 95% CI, 1.226-3.701, P=0.007; oral corticosteroid: OR, 1.932; 95% CI, 1.66-2.25, P<0.001; non-steroid bronchodilator: OR, 2.849; 95% CI, 2.48-3.273, P<0.001). A graded association with AF risk was also observed among subjects treated with ICS or bronchodilator.

CONCLUSIONS

Asthma was associated with an increased risk of developing future AF.

Improving asthma during pregnancy with dietary antioxidants: the current evidence

The complication of asthma during pregnancy is associated with a number of poor outcomes for the mother and fetus. This may be partially driven by increased oxidative stress induced by the combination of asthma and pregnancy. Asthma is a chronic inflammatory disease of the airways associated with systemic inflammation and oxidative stress, which contributes to worsening asthma symptoms. Pregnancy alone also intensifies oxidative stress through the systemic generation of excess reactive oxidative species (ROS). Antioxidants combat the damaging effects of ROS; yet antioxidant defenses are reduced in asthma. Diet and nutrition have been postulated as potential factors to combat the damaging effects of asthma. In particular, dietary antioxidants may play a role in alleviating the heightened oxidative stress in asthma. Although there are some observational and interventional studies that have shown protective effects of antioxidants in asthma, assessment of antioxidants in pregnancy are limited and there are no antioxidant intervention studies in asthmatic pregnancies on asthma outcomes. The aims of this paper are to (i) review the relationships between oxidative stress and dietary antioxidants in adults with asthma and asthma during pregnancy, and (ii) provide the rationale for which dietary management strategies, specifically increased dietary antioxidants, might positively impact maternal asthma outcomes. Improving asthma control through a holistic antioxidant dietary approach might be valuable in reducing asthma exacerbations and improving asthma management during pregnancy, subsequently impacting perinatal health.

Oxidative stress and antioxidant deficiencies in asthma: potential modification by diet

The lungs of asthmatic patients are exposed to oxidative stress due to the generation of reactive oxygen and nitrogen species as a consequence of chronic airway inflammation. Increased concentrations of NO*, H2O2 and 8-isoprostane have been measured in exhaled breath and induced sputum of asthmatic patients. O2*-, NO*, and halides interact to form highly reactive species such as peroxynitrite and HOBr, which in turn cause nitration and bromination of protein tyrosine residues. Oxidative stress may also reduce glutathione levels and cause inactivation of antioxidant enzymes such as superoxide dismutase, with a consequent increase in apoptosis, shedding of airway epithelial cells and airway remodelling. The oxidant/antioxidant equilibrium in asthmatic patients may be further perturbed by low dietary intakes of the antioxidant vitamins C and E, selenium and flavonoids, with a consequent lowering of the concentrations of these and other non-dietary antioxidants such as bilirubin and albumin in plasma and airway epithelial lining fluid. Although supplementation with vitamins C and E appears to offer protection against the adverse effects of ozone, recent randomised, placebo-controlled trials of vitamin C or E supplements for patients with mild asthma have not shown significant benefits over standard therapy. However, genetic variation in glutathione S-transferase may influence the susceptibility of asthmatic individuals to oxidative stress and the extent to which they are likely to benefit from antioxidant supplementation. Long-term prospective trials are required to determine whether modification of dietary intake will benefit asthma patients and reduce the socio-economic burden of asthma in the community.

Nutritional supplements and plasma antioxidants in childhood asthma

OBJECTIVE

This study investigated the relationship of plasma antioxidants to airway inflammation and systemic oxidative stress in children suffering from atopic asthma with consideration of the intake of nutritional supplements.

SUBJECTS AND RESEARCH METHODS

A total of 35 asthmatic children (AG) and 21 healthy controls (CG) participated in this study. Plasma levels of vitamins A and E, β-carotene, coenzyme Q10 and malondialdehyde (MDA) were analyzed with high-performance liquid chromatography (HPLC); the total antioxidant capacity (TAC) was measured photometrically, and selenium was determined by atomic absorption spectroscopy (AAS). The volume of fractionated exhaled nitric oxide (FeNO) was measured with the NIOX nitric oxide monitoring system.

RESULTS

The plasma antioxidants vitamins A and E, selenium, and coenzyme Q10 but not β-carotene were significantly (p < 0.05) lower in asthmatics than in controls. Further, asthmatic children had significantly reduced plasma concentrations of TAC (p < 0.01), significantly enhanced levels of MDA (p < 0.001), and exhaled a significantly (p < 0.001) higher mean volume of FENO than healthy children. Regular intake of supplements had a significant positive influence on plasma vitamin E (p < 0.01), selenium (p < 0.01), TAC (p < 0.05), MDA (p < 0.01), and FENO (p < 0.01) in asthmatics but not in controls. Additionally, significant negative associations of vitamin E and MDA (AG: p < 0.01; CG: p < 0.05), and vitamin E and FENO (AG: p < 0.05; CG: p > 0.05) were identified.

CONCLUSION

These results indicate that nutritional supplements beneficially modulate plasma antioxidants and thus might have a positive influence on systemic redox balance and subsequently, pulmonary inflammation in asthmatic children.

Changes in Several Inflammatory and Oxidation Markers after Ovalbumin-Sensitization in a Guinea Pig Model of Allergic Asthma - A Pilot Study

Ovalbumin (OVA)-sensitization is a common way to evoke changes similar to changes in allergic asthma in humans. Activated cells produce various pro-inflammatory and vasoactive substances including reactive oxygen species. The goal of this pilot study was to evaluate mobilization of leukocytes into the lungs and oxidation processes induced by OVA-sensitization in a guinea-pig model of allergic asthma. Guinea-pigs were divided into OVA-sensitized and naïve animals. After sacrificing animals, blood samples were taken and total and differential leukocyte counts were calculated, and eosinophil cationic protein (ECP) and total antioxidant status (TAS) in the plasma were determined. Left lungs were saline-lavaged and total number of cells and differential leukocyte count in the bronchoalveolar lavage fluid (BAL) were calculated. Right lung tissue was homogenized, ECP, TAS and products of lipid and protein oxidation (thiobarbituric acid-reactive substances and lysine-lipoperoxidation end-products) were determined in the lung homogenate. OVA-sensitization increased a total number of cells and percentages of eosinophils and neutrophils and slightly increased ECP in the blood and in the BAL fluid. In addition, increased lipid and protein oxidation in the lung homogenate, and decreased TAS in the plasma was found in OVA-sensitized compared to naïve animals. In conclusion, OVA-sensitization increased mobilization of leukocytes into the lungs and elevated production of reactive oxygen spesies (ROS), accompanied by a decrease in plasma TAS.

Glutathione redox control of asthma: from molecular mechanisms to therapeutic opportunities

Asthma is a chronic inflammatory disorder of the airways associated with airway hyper-responsiveness and airflow limitation in response to specific triggers. Whereas inflammation is important for tissue regeneration and wound healing, the profound and sustained inflammatory response associated with asthma may result in airway remodeling that involves smooth muscle hypertrophy, epithelial goblet-cell hyperplasia, and permanent deposition of airway extracellular matrix proteins. Although the specific mechanisms responsible for asthma are still being unraveled, free radicals such as reactive oxygen species and reactive nitrogen species are important mediators of airway tissue damage that are increased in subjects with asthma. There is also a growing body of literature implicating disturbances in oxidation/reduction (redox) reactions and impaired antioxidant defenses as a risk factor for asthma development and asthma severity. Ultimately, these redox-related perturbations result in a vicious cycle of airway inflammation and injury that is not always amenable to current asthma therapy, particularly in cases of severe asthma. This review will discuss disruptions of redox signaling and control in asthma with a focus on the thiol, glutathione, and reduced (thiol) form (GSH). First, GSH synthesis, GSH distribution, and GSH function and homeostasis are discussed. We then review the literature related to GSH redox balance in health and asthma, with an emphasis on human studies. Finally, therapeutic opportunities to restore the GSH redox balance in subjects with asthma are discussed.

NADPH oxidase-derived ROS and the regulation of pulmonary vessel tone

Pulmonary vessel constriction results from an imbalance between vasodilator and vasoconstrictor factors released by the endothelium including nitric oxide, endothelin, prostanoids, and reactive oxygen species (ROS). ROS, generated by a variety of enzymatic sources (such as mitochondria and NADPH oxidases, a.k.a. Nox), appear to play a pivotal role in vascular homeostasis, whereas elevated levels effect vascular disease. The pulmonary circulation is very sensitive to changes in the partial pressure of oxygen and differs from the systemic circulation in its response to this change. In fact, the pulmonary vessels contract in response to low oxygen tension, whereas systemic vessels dilate. Growing evidence suggests that ROS production and ROS-related pathways may be key factors that underlie this differential response to oxygen tension. A major emphasis of our laboratory is the role of Nox isozymes in cardiovascular disease. In this review, we will focus our attention on the role of Nox-derived ROS in the control of pulmonary vascular tone.

Pathogenesis and disease mechanisms of occupational asthma

Occupational asthma (OA) is one of the most common forms of work-related lung disease in all industrialized nations. The clinical management of patients with OA depends on an understanding of the multifactorial pathogenetic mechanisms that can contribute to this disease. This article discusses the various immunologic and nonimmunologic mechanisms and genetic susceptibility factors that drive the inflammatory processes of OA.

Hyperoxidized peroxiredoxins in peripheral blood mononuclear cells of asthma patients is associated with asthma severity

AIMS

Oxidative stress is involved in the pathogenesis of asthma, and peroxiredoxins (PRDX) may be critical in controlling intracellular oxidative stress. The aim of this study was to evaluate expressions of PRDX and their hyperoxidized forms in asthmatic individuals.

MAIN METHODS

The levels of expression of PRDX1, PRDX2, PRDX3, and PRDX6 and their hyperoxidized forms (PRDX-SO(3)) were measured in PBMCs from asthma patients and control subjects. In addition, cells from these subjects were treated with hydrogen peroxide (H(2)O(2)) and their intracellular concentrations of reactive oxygen species (ROS) were measured.

KEY FINDINGS

The ratios of hyperoxidized to total PRDX (PRDX-SO(3/)PRDX) in PBMCs were significantly higher in asthma patients than in normal subjects and were correlated with disease severity, with the highest ratio seen in patients with severe asthma. Furthermore, H(2)O(2) treatment of PBMCs, particularly lymphocytes, increased intracellular ROS concentrations with greater and more persistent increases observed in cells from asthmatic than from control subjects.

SIGNIFICANCE

Hyperoxidation of PRDX may serve as a biomarker of asthma severity and may predict enhanced susceptibility to oxidative stress load in PBMCs of asthmatics.

Nitric oxide metabolism in asthma pathophysiology

BACKGROUND

Asthma, a chronic inflammatory disease is typically characterized by bronchoconstriction and airway hyper-reactivity.

SCOPE OF REVIEW

A wealth of studies applying chemistry, molecular and cell biology to animal model systems and human asthma over the last decade has revealed that asthma is associated with increased synthesis of the gaseous molecule nitric oxide (NO).

MAJOR CONCLUSION

The high NO levels in the oxidative environment of the asthmatic airway lead to greater formation of reactive nitrogen species (RNS) and subsequent oxidation and nitration of proteins, which adversely affect protein functions that are biologically relevant to chronic inflammation. In contrast to the high levels of NO and nitrated products, there are lower levels of beneficial S-nitrosothiols (RSNO), which mediate bronchodilation, due to greater enzymatic catabolism of RSNO in the asthmatic airways.

GENERAL SIGNIFICANCE

This review discusses the rapidly accruing data linking metabolic products of NO as critical determinants in the chronic inflammation and airway reactivity of asthma. This article is part of a Special Issue entitled Biochemistry of Asthma.

Altered oxidative state in schoolchildren with asthma and allergic rhinitis

Oxidative stress may be defined as a disruption of the balance between the level of oxidants and reductants (antioxidants), and oxidative state in children may influence the risk of asthma and allergic disease. We investigated serum antioxidant levels: selenium, vitamin E, bilirubin, albumin, uric acid and transferrin as well as the oxidant ferritin and their association with asthma and allergic rhinitis. Children of 7-12 yr with asthma (n = 50) and no asthma (controls) (n = 52) underwent skin prick test, lung function, fractional exhaled nitric oxide (FeNO) measurements and blood sampling. Allergic rhinitis was found in 23 children, 19 with asthma and four controls. Healthy children were controls without rhinitis. Asthma was associated with reduced albumin (g/l), adjusted odds ratio (aOR) (95% CI) 0.81 (0.66, 0.99) (p = 0.048) compared with healthy children in a regression analysis adjusted for age and gender. Asthma with high FeNO ≥20 ppb was associated with reduced albumin, aOR 0.60 (0.40, 0.89) (p = 0.012) compared to controls with FeNO <20. Asthma with allergic rhinitis had reduced albumin, aOR = 0.70 (0.50, 0.99) (p = 0.04), and higher ferritin levels (mg/l) [aOR = 1.04 (1.00, 1.09) p = 0.03] compared to healthy children. Poorly controlled asthma was associated with lower vitamin E levels, aOR 0.79 (0.65, 0.95) (p = 0.02), lower transferrin levels, aOR 0.72 (0.57, 0.92) (p < 0.01), and higher albumin levels, aOR 1.53 (1.03, 2.28) (p = 0.04), compared to well controlled asthma. In conclusion, schoolchildren with asthma and rhinitis had reduced levels of the major serum antioxidant albumin, and poorly controlled asthma was associated with decreased vitamin E and transferrin levels. Reduced albumin was associated with increased FeNO, a marker of allergic inflammation in asthma, although the discriminatory value of this finding should be further assessed in population studies.

Glutathione biochemistry in asthma

BACKGROUND

Oxidative stress in an important hallmark of asthma and much research has therefore focused on the predominant antioxidant in the lungs, namely the tripeptide glutathione.

MAJOR CONCLUSIONS

In lung samples of patients with asthma increased levels of glutathione are typically observed, which appear to relate to the level of pulmonary inflammation and are therefore regarded as an adaptive response to the associated oxidative stress. Also in blood samples increased total GSH levels have been reported, representing the systemic inflammatory component of the disease. In addition, a number of the antioxidant enzymes involved in the maintenance of the GSH/GSSG ratio as well as enzymes that utilize GSH have been found to be altered in the lungs and blood of asthmatics and will be summarized in this review. Very few studies have however linked enzymatic alterations to GSH levels or found that either of these correlated with disease severity. Some animal studies have started to investigate the pathophysiological role of GSH biochemistry in asthma and have yielded surprising results. Important in this respect is the physiological role of the GSH redox equilibrium in determining the outcome of immune responses, which could be deregulated in asthmatics and contribute to the disease.

SCOPE OF REVIEW

Clinical data as well as animal and cell culture studies regarding these aspects of GSH in the context of asthma will be summarized and discussed in this review. This article is part of a Special Issue entitled: Biochemistry of Asthma.

The role of oxidative stress in the pathogenesis of asthma

Oxidative stress plays a critical role in the pathogenesis of asthma. To effectively control oxidative stress in asthmatics, it is important to investigate the precise intracellular mechanism by which the development of immunity, rather than immune tolerance and progression of airway inflammation, is induced. In this article, we suggest that protein tyrosine phosphatases, as intracellular negative regulators, and intracellular antioxidant enzymes such as peroxiredoxins can be regulated by oxidative stress during intracellular signaling.

Obesity, asthma, and oxidative stress

Obesity is associated with increased systemic and airway oxidative stress, which may result from a combination of adipokine imbalance, comorbidities, and reduced antioxidant defenses. While obesity-mediated increased oxidative stress plays an important role in the pathogenesis of vascular disease and nonalcoholic hepatic steatosis, little is known of how it may affect the lung. Contrary to what has previously been thought, the combination of obesity and asthma, both chronic inflammatory diseases, does not necessarily result in a synergistic effect, leading to even greater oxidative stress. However, most available studies have compared the levels of oxidative stress biomarkers on stable asthma patients, and it is possible that the interaction of oxidative stress between obesity and asthma is not readily detectable under basal conditions. We propose that obesity-mediated oxidative stress, which may affect the lung function of asthmatic subjects by increasing airway inflammation and reducing the effectiveness of inhaled corticosteroids, may become evident during exposure to an aggravating factor or during periods of asthma exacerbation. Understanding whether obesity-mediated oxidative stress has a mechanistic role in the association between obesity and asthma will help in the formation of public health policies and increase our capacity to develop therapeutic interventions that improve the life of obese asthmatic subjects.

Obesity-asthma association: is it explained by systemic oxidant stress?

BACKGROUND

The mechanism for the obesity-asthma association is unknown. This study evaluated the hypothesis that systemic oxidant stress explains this association.

METHODS

This cross-sectional study used year-20 follow-up evaluation data of 2,865 eligible participants in the Coronary Artery Risk Development in Young Adults (CARDIA) cohort. Current asthma was self-reported. Oxidant stress primarily was assessed by plasma F2-isoprostane concentrations. Obesity measures included categories of BMI and dual-energy x-ray absorptiometry-assessed fat mass index (FMI) and lean mass index (LMI). Logistic and linear regressions were used for analyses.

RESULTS

Asthma was associated with higher plasma F2-isoprostane concentrations (p = 0.049); however, this association was not significant when adjusted for either gender or BMI. The BMI-asthma association was seen only among women (p = 0.03; gender-specific interaction, p = 0.01), and this association was not explained by plasma F2-isoprostane levels. Similarly, both FMI and LMI were positively associated with asthma in women (p = 0.20 and 0.01, respectively). These associations also were not explained by plasma F2-isoprostane levels. Similar results were obtained when plasma levels of oxidized low-density lipoprotein were used instead of F2-isoprostane levels to study the BMI-asthma association at the year-15 evaluation.

CONCLUSIONS

Systemic oxidant stress, primarily assessed by plasma F2-isoprostane concentrations, was not independently associated with asthma and, therefore, may not explain the obesity-asthma association in women. The asthma-oxidant stress association is confounded by gender and obesity. This study is limited by the inability to measure airway oxidant stress. It is possible that another (as yet undetermined) measure of systemic oxidant stress may be more relevant in asthma.

Sex determines the influence of smoking and gene polymorphism on glutathione peroxidase activity in erythrocytes

OBJECTIVE

Glutathione peroxidase 1 (GPX1) is one of the major oxidative enzymes. Our aim was to characterize factors influencing its activity and to determine whether or not the activity is associated with asthma.

MATERIAL AND METHODS

Serum selenium concentration was measured, GPX1 polymorphisms were genotyped and smoking history was obtained in a Danish population-derived case-base cohort of 1,191 subjects designed to evaluate risk factors for asthma. GPX1 activity was measured in 134 male and 164 female subjects equally distributed according to genotype of GPX1. Among these subjects, 82 (28 %) had doctor-diagnosed asthma.

RESULTS

The average serum selenium concentration was too low for optimal enzyme activity (mean (SE), 83.4 (0.76) ng/mL). GPX1 activity in men was lower than in women, 52.6 (0.66) and 56.4 (0.59) U/g protein, respectively (p<0.001). In men, activity was positively associated with serum selenium concentration (p = 0.005) and negatively associated with both active smoking (p = 0.009) and exposure to environmental tobacco smoke (p = 0.02). In women, activity was associated with genotypes with 59.2 (1.4), 56.0 (1.4) and 54.2 (1.4) U/g protein in the homozygote wild-type, the heterozygote and the homozygote variant type, respectively (p = 0.001). Doctor-diagnosed asthma was unrelated to GPX1 activity in either sex.

CONCLUSION

Determinants for activity in the oxidative enzyme GPX1 show marked differences between the sexes, but the activity is not associated with asthma. Sex ought to be taken into consideration when analysing the activity of the enzyme.

Oxidant--antioxidant imbalance in asthma: scientific evidence, epidemiological data and possible therapeutic options

Prevalence of asthma has increased considerably in recent decades throughout the world especially in developed countries. Airway inflammation is thought to be prime cause for repeated episodes of airway obstruction in asthmatics. Several studies have shown that reactive oxygen species (ROS) play a key role in initiation as well as amplification of inflammation in asthmatic airways. Excessive ROS production in asthma leads to alteration in key enzymatic as well as nonenzymatic antioxidants such as glutathione, vitamins C and E, beta-carotene, uric acid, thioredoxin, superoxide dismutases, catalase, and glutathione peroxidases leading to oxidant-antioxidant imbalance in airways. Oxidant-antioxidant imbalance leads to pathophysiological effects associated with asthma such as vascular permeability, mucus hypersecretion, smooth muscle contraction, and epithelial shedding. Epidemiological data also support the scientific evidence of oxidant-antioxidant imbalance in asthmatics. Therefore, the supplementation of antioxidants to boost the endogenous antioxidants or scavenge excessive ROS production could be utilized to dampen/prevent the inflammatory response in asthma by restoring oxidant-antioxidant balance. This review summarizes the scientific and epidemiological evidence linking asthma with oxidant-antioxidant imbalance and possible antioxidant strategies that can be used therapeutically for better management of asthma.

Evaluation of whole antioxidant defenses of human mononuclear cells by a new in vitro biological test: lack of correlation between erythrocyte and mononuclear cell resistance to oxidative stress

OBJECTIVES

This work aims to evaluate the resistance of mononuclear cells to oxidative stress using a "KRL" test, formerly utilized to evaluate the resistance of erythrocyte to free radicals.

METHODS

The "KRL" test evaluates the resistance to lysis of cells treated by free radicals generated under standardized conditions.

RESULTS

We defined new analytical parameters (level of radical production, time course, number of cells) to obtain an accurate assay determining the resistance to oxidative stress of mononuclear cells, in comparison to that of erythrocytes. This test allows the evaluation of change in the redox state of mononuclear cells (improved by an antioxidant mix or deteriorated by antimycin A-induced mitochondrial radical overproduction). Interestingly, our data show that the sensitivity of mononuclear cells to oxidative stress is not correlated with the susceptibility of erythrocytes to oxidative stress.

CONCLUSIONS

The quantification of the susceptibility of mononuclear cells to oxidative stress gives additional information (in addition to erythrocyte resistance) and could be helpful for patients with chronic inflammation.

Glutathione peroxidase enzyme activity in aging

BACKGROUND

It is hypothesized that free radical damage contributes to aging. Age-related decline in activity of the antioxidant enzyme glutathione peroxidase (GPx) may contribute to increased free radicals. We hypothesized that GPx activity decreases with age in a population of older women with disability.

METHODS

Whole blood GPx activity was measured in baseline stored samples from participants in the Women's Health and Aging Study I, a cohort of disabled community-dwelling older women. Linear regression was used to determine cross-sectional associations between GPx activity and age, adjusting for hemoglobin, coronary disease, diabetes, selenium, and body mass index.

RESULTS

Six hundred one participants had complete demographic, disease, and laboratory information. An inverse association was observed between GPx and age (regression coefficient = -2.9, p <.001), indicating that for each 1-year increase in age, GPx activity decreased by 2.9 micromol/min/L. This finding remained significant after adjustment for hemoglobin, coronary disease, diabetes, and selenium, but not after adjustment for body mass index and weight loss.

CONCLUSION

This is the first study to examine the association between age and GPx activity in an older adult cohort with disability and chronic disease. These findings suggest that, after age 65, GPx activity declines with age in older women with disability. This decline does not appear to be related to diseases that have been previously reported to alter GPx activity. Longitudinal examination of GPx activity and other antioxidant enzymes in diverse populations of older adults will provide additional insight into age- and disease-related changes in these systems.

Increase in reactive oxygen metabolite level in acute exacerbations of asthma

BACKGROUND

Oxidants including reactive oxygen species have been indicated to play an important role in the pathogenesis of asthma.

OBJECTIVE

We investigated oxidative status in patients with acute exacerbations of asthma and evaluated the therapeutic response using the D-ROM test which is simple to use and quick.

METHODS

We measured reactive oxygen metabolite (ROM) levels in the serum of 42 outpatients with acute exacerbations of asthma, 11 outpatients with stable asthma and 40 healthy subjects using the D-ROM test. Seven inpatients admitted due to acute exacerbations of asthma were also enrolled to evaluate the effects of treatment. Serum eosinophil cationic protein and plasma polymorphonuclear elastase were also measured by EIA or ELISA to evaluate the correlation between inflammation and oxidative status.

RESULTS

Serum ROM levels were significantly higher in patients with acute exacerbation of asthma than in patients with stable asthma or healthy subjects. Levels of serum eosinophil cationic protein and plasma polymorphonuclear elastase were increased in acute exacerbation and moderately correlated to ROM levels. Levels of ROM were significantly decreased after treatment with systemic steroids and bronchodilators.

CONCLUSION

These findings suggest that acute exacerbation of asthma is associated with increased oxidative stress. Serum ROM levels would partly reflect the inflammation with eosinophils and neutrophils and may be useful as biomarkers of asthma.

Role of pollen NAD(P)H oxidase in allergic inflammation

PURPOSE OF REVIEW

Plant pollens are one of the most common outdoor allergens. Pollen grains and subpollen particles can reach lower airways and induce symptoms of seasonal asthma and allergic rhinitis. Plants possess NAD(P)H oxidase activity that generates reactive oxygen species for physiological functions such as root-hair and pollen-tube growth, defense against microbial infections and cell signaling. The presence of NAD(P)H oxidases in pollens and their role in induction of airway inflammation have not been described until recently.

RECENT FINDINGS

We discovered the presence of NAD(P)H oxidase in ragweed and other plant pollens. These oxidases induce reactive oxygen species in mucosal cells (signal 1) independent of adaptive immunity. This reactive oxygen species facilitates antigen (signal 2)-induced allergic inflammation. Inhibiting signal 1 by administration of antioxidants attenuated ragweed extract-induced allergic inflammation. Likewise, abrogating signal 2 by antigen challenge in mice lacking T cells failed to induce allergic inflammation.

SUMMARY

Reactive oxygen species generated by pollen NAD(P)H oxidase play a major role in pathogenesis of allergic airway inflammation and airway hypersensitivity. Based on our findings, we propose a 'two signal hypothesis of allergic inflammation' in which both signal 1 (reactive oxygen species) and signal 2 (antigen presentation) are required in order to induce full-blown allergic inflammation.

Redox cycling of 9,10-phenanthraquinone to cause oxidative stress is terminated through its monoglucuronide conjugation in human pulmonary epithelial A549 cells

9,10-Phenanthraquinone (PQ), a component of airborne particulate matter, causes marked cellular protein oxidation and cytotoxicity through a two-electron reduction to 9,10-dihydroxyphenanthrene (PQH2), which is associated with the propagation of reactive oxygen species (K. Taguchi et al., Free Radic. Biol. Med. 43:789-799, 2007). In the present study, we explored a biotransformation pathway for the detoxification of PQ. Exposure of human pulmonary epithelial A549 cells to PQ resulted in a time-dependent appearance of an unknown metabolite in the medium that was identified as the monoglucuronide of PQH2 (PQHG). Whereas a variety of isozymes of uridine 5'-diphosphate glucuronosyltransferase (UGTs) are responsible for PQHG formation, UGT1A10 and UGT1A6 were particularly effective catalysts for glucuronide conjugation. In cell-free systems, PQ exhibited a rapid thiol oxidation and subsequent oxygen consumption in the presence of dithiothreitol, whereas PQHG did not. Unlike the parent compound, PQHG completely lost the ability to oxidize cellular proteins and cause cell death in A549 cells. In addition, deletion of the transcription factor Nrf2 decreased PQHG formation and increased PQ-mediated toxicity of mouse primary hepatocytes. Thus, we conclude that PQHG is a metabolite of PQ, generated through PQH2, that terminates its redox cycling and transports it to extracellular space.

Psychological factors in asthma

Asthma has long been considered a condition in which psychological factors have a role. As in many illnesses, psychological variables may affect outcome in asthma via their effects on treatment adherence and symptom reporting. Emerging evidence suggests that the relation between asthma and psychological factors may be more complex than that, however. Central cognitive processes may influence not only the interpretation of asthma symptoms but also the manifestation of measurable changes in immune and physiologic markers of asthma. Furthermore, asthma and major depressive disorder share several risk factors and have similar patterns of dysregulation in key biologic systems, including the neuroendocrine stress response, cytokines, and neuropeptides. Despite the evidence that depression is common in people with asthma and exerts a negative impact on outcome, few treatment studies have examined whether improving symptoms of depression do, in fact, result in better control of asthma symptoms or improved quality of life in patients with asthma.

Elevated plasma glutathione peroxidase concentration in acute severe asthma: comparison with plasma glutathione peroxidase activity, selenium and malondialdehyde

OBJECTIVE

To investigate plasma glutathione peroxidase concentration, glutathione peroxidase activity, plasma selenium and oxidative stress in acute severe asthma.

MATERIAL AND METHODS

The study was case-control in design, with cases presenting to the emergency department with acute severe asthma and controls randomly selected from a larger cross-sectional study. Plasma malondialdehyde (MDA) was used as a measure of oxidative stress and plasma selenium was measured using ICP-MS. Glutathione peroxidase (GPx) activity was analysed using a colorimetric GPx assay and plasma GPx level was measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Fifteen cases [mean (range) predicted peak expiratory flow rate (PEFR) of 43% (20-69)] and 15 matched controls were recruited. MDA levels (mean+/-SD) were higher in acute asthma subjects (1.30+/-0.56 micromol/L) than in controls (0.86+/-0.53 micromol/L; p<0.05). There were no differences between cases and controls for selenium (99+/-34 microg/L versus 109+/-17 microg/L) or for GPx activity (39+/-25 nmol min(-1) mL(-1) versus 38+/-24 nmol min(-1) mL(-1)), however, GPx plasma levels measured by ELISA were higher in cases than controls (22.5+/-10.8 mg/L versus 13.8+/-7.3 mg/L; p<0.05).

CONCLUSIONS

Patients with acute severe asthma demonstrated increased MDA levels but no differences in plasma selenium levels or GPx activity. GPx levels measured by ELISA were elevated in severe asthma. These results are consistent with an adaptive up-regulation of GPx to protect against oxidative stress.

Comparison of changes in erythrocyte and platelet phospholipid and fatty acid composition and protein oxidation in chronic obstructive pulmonary disease and asthma

OBJECTIVE

To analyse and compare the phospholipid and fatty acid composition of total lipids and the occurrence of lipid peroxidation and protein oxidation directly in erythrocytes or platelets from chronic obstructive pulmonary disease (COPD) and asthma patients.

PATIENTS

Fifteen consecutive outpatients with COPD (all smokers) and asthma (non-smokers) recruited during a moderate-to-severe (COPD) or moderate (asthma) exacerbation. Fifteen subjects with smoking habits similar to those of COPD patients were studied as a control group.

METHODS

Phospholipid and total fatty acid compositions were analysed by two-dimensional thin layer chromatography or gas chromatography-mass spectrometry, respectively. The lipid fluorescence of lipid extracts was measured by spectrofluorimetry. Protein carbonyl contents and profiles were measured by immunoblot detection.

RESULTS

No differences were found either in erythrocyte or platelet cholesterol or phospholipid levels. Only a decrease in the content of phosphatidylserine + phosphatidylinositol (P<0.003) was detected in platelets from the asthma patients. In erythrocytes, the fatty acid profile changed in both lung pathologies, especially as regards polyunsaturated fatty acids (decreases in arachidonic and 22:4 fatty acid contents). Other observed changes were: COPD, an increase in palmitic fatty acid; asthma, an increase in oleic and decreases in eicosapentaenoic and 22:6 + 24:1 fatty acids. In platelets, the fatty acid profiles revealed many differences between both lung pathologies: COPD, a decrease in 18:1 and increases in 20:5 and 22:5 + 24:0; asthma, a decrease in 20:4 and increase in 22:6 + 24:1. In COPD vs. asthma patients, fatty acid changes were mainly detected in platelets, especially in 18-carbon species, with decreases in stearic and 18:1 fatty acids in the COPD patients. Protein oxidation levels were increased in both lung pathologies in both erythrocytes and platelets.

CONCLUSIONS

COPD and asthma are associated with common or specific changes in the lipid composition of erythrocytes and/or platelets. The data point to lipid peroxidation and protein oxidation phenomena in both types of blood cell, although platelets would be more susceptible to stress.

Catalase overexpression fails to attenuate allergic airways disease in the mouse

Oxidative stress is a hallmark of asthma, and increased levels of oxidants are considered markers of the inflammatory process. Most studies to date addressing the role of oxidants in the etiology of asthma were based on the therapeutic administration of low m.w. antioxidants or antioxidant mimetic compounds. To directly address the function of endogenous hydrogen peroxide in the pathophysiology of allergic airway disease, we comparatively evaluated mice systemically overexpressing catalase, a major antioxidant enzyme that detoxifies hydrogen peroxide, and C57BL/6 strain matched controls in the OVA model of allergic airways disease. Catalase transgenic mice had 8-fold increases in catalase activity in lung tissue, and had lowered DCF oxidation in tracheal epithelial cells, compared with C57BL/6 controls. Despite these differences, both strains showed similar increases in OVA-specific IgE, IgG1, and IgG2a levels, comparable airway and tissue inflammation, and identical increases in procollagen 1 mRNA expression, following sensitization and challenge with OVA. Unexpectedly, mRNA expression of MUC5AC and CLCA3 genes were enhanced in catalase transgenic mice, compared with C57BL/6 mice subjected to Ag. Furthermore, when compared with control mice, catalase overexpression increased airway hyperresponsiveness to methacholine both in naive mice as well as in response to Ag. In contrast to the prevailing notion that hydrogen peroxide is positively associated with the etiology of allergic airways disease, the current findings suggest that endogenous hydrogen peroxide serves a role in suppressing both mucus production and airway hyperresponsiveness.

Enhanced airway reactivity and inflammation in A2A adenosine receptor-deficient allergic mice

A(2A) adenosine receptor (A(2A)AR) has potent anti-inflammatory properties, which may be important in the regulation of airway reactivity and inflammation. Inflammatory cells that possess A(2A)AR also produce nitrosative stress, which is associated with pathophysiology of asthma, so we hypothesized that A(2A)AR deficiency may lead to increased airway reactivity and inflammation through nitrosative stress. Thus the present study was carried out to investigate the role of A(2A)AR on airway reactivity, inflammation, NF-kappaB signaling, and nitrosative stress in A(2A)AR knockout (KO) and wild-type (WT) mice using our murine model of asthma. Animals were sensitized intraperitoneally on days 1 and 6 with 200 microg of ragweed, followed by aerosolized challenges with 0.5% ragweed on days 11, 12, and 13, twice a day. On day 14, airway reactivity to methacholine was assessed as enhanced pause (Penh) using whole body plethysmography followed by bronchoalveolar lavage (BAL) and lung collection for various analyses. Allergen challenge caused a significant decrease in expression of A(2A)AR in A(2A) WT sensitized mice, with A(2A)AR expression being undetected in A(2A) KO sensitized group leading to decreased lung cAMP levels in both groups. A(2A)AR deletion/downregulation led to an increase in Penh to methacholine and influx of total cells, eosinophils, lymphocytes, and neutrophils in BAL with highest values in A(2A) KO sensitized group. A(2A) KO sensitized group further had increased NF-kappaB expression and nitrosative stress compared with WT sensitized group. These data suggest that A(2A)AR deficiency leads to airway inflammation and airway hyperresponsiveness, possibly via involvement of nitrosative stress in this model of 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.

Oxidative stress in asthma and COPD: antioxidants as a therapeutic strategy

Asthma and chronic obstructive pulmonary disease (COPD) are inflammatory lung diseases that are characterized by systemic and chronic localized inflammation and oxidative stress. Sources of oxidative stress arise from the increased burden of inhaled oxidants, as well as elevated amounts of reactive oxygen species (ROS) released from inflammatory cells. Increased levels of ROS, either directly or via the formation of lipid peroxidation products, may play a role in enhancing the inflammatory response in both asthma and COPD. Moreover, in COPD it is now recognized as the main pathogenic factor for driving disease progression and increasing severity. ROS and lipid peroxidation products can influence the inflammatory response at many levels through its impact on signal transduction mechanisms, activation of redox-sensitive transcriptions factors, and chromatin regulation resulting in pro-inflammatory gene expression. It is this impact of ROS on chromatin regulation by reducing the activity of the transcriptional co-repressor, histone deacetylase-2 (HDAC-2), that leads to the poor efficacy of corticosteroids in COPD, severe asthma, and smoking asthmatics. Thus, the presence of oxidative stress has important consequences for the pathogenesis, severity, and treatment of asthma and COPD. However, for ROS to have such an impact, it must first overcome a variety of antioxidant defenses. It is likely, therefore, that a combination of antioxidants may be effective in the treatment of asthma and COPD. Various approaches to enhance the lung antioxidant screen and clinical trials of antioxidant compounds are discussed.