Oxidants and the pathogenesis of lung diseases

NLRP3 inflammasome activation by mitochondrial ROS in bronchial epithelial cells is required for allergic inflammation

Abnormality in mitochondria has been suggested to be associated with development of allergic airway disorders. In this study, to evaluate the relationship between mitochondrial reactive oxygen species (ROS) and NLRP3 inflammasome activation in allergic asthma, we used a newly developed mitochondrial ROS inhibitor, NecroX-5. NecroX-5 reduced the increase of mitochondrial ROS generation in airway inflammatory cells, as well as bronchial epithelial cells, NLRP3 inflammasome activation, the nuclear translocation of nuclear factor-κB, increased expression of various inflammatory mediators and pathophysiological features of allergic asthma in mice. Finally, blockade of IL-1β substantially reduced airway inflammation and hyperresponsiveness in the asthmatic mice. These findings suggest that mitochondrial ROS have a critical role in the pathogenesis of allergic airway inflammation through the modulation of NLRP3 inflammasome activation, providing a novel role of airway epithelial cells expressing NLRP3 inflammasome as an immune responder.

NLRP3 inflammasome activation by mitochondrial ROS in bronchial epithelial cells is required for allergic inflammation

Abnormality in mitochondria has been suggested to be associated with development of allergic airway disorders. In this study, to evaluate the relationship between mitochondrial reactive oxygen species (ROS) and NLRP3 inflammasome activation in allergic asthma, we used a newly developed mitochondrial ROS inhibitor, NecroX-5. NecroX-5 reduced the increase of mitochondrial ROS generation in airway inflammatory cells, as well as bronchial epithelial cells, NLRP3 inflammasome activation, the nuclear translocation of nuclear factor-κB, increased expression of various inflammatory mediators and pathophysiological features of allergic asthma in mice. Finally, blockade of IL-1β substantially reduced airway inflammation and hyperresponsiveness in the asthmatic mice. These findings suggest that mitochondrial ROS have a critical role in the pathogenesis of allergic airway inflammation through the modulation of NLRP3 inflammasome activation, providing a novel role of airway epithelial cells expressing NLRP3 inflammasome as an immune responder.

Disease models of chronic inflammatory airway disease: applications and requirements for clinical trials

PURPOSE OF REVIEW

This review will discuss methodologies and applicability of key inflammatory models of respiratory disease in proof of concept or proof of efficacy clinical studies. In close relationship with these models, induced sputum and inflammatory cell counts will be addressed for phenotype-directed drug development. Additionally, important regulatory aspects regarding noninvestigational medicinal products used in bronchial challenges or clinical inflammatory models of respiratory disease will be highlighted.

RECENT FINDINGS

The recognition of an ever increasing number of phenotypes and endotypes within conditions such as asthma and chronic obstructive pulmonary disease urges phenotyping of study populations already in early clinical phases of drug development. Apart from the choice of a relevant disease model, recent studies show that especially targeted therapies need to be tested in well defined disease subsets for adequate efficacy assessment. Noninvasive biomarkers, especially sputum inflammatory cell counts, aid phenotyping and are useful outcome measures for novel, targeted therapies.

SUMMARY

Disease phenotyping becomes increasingly important for efficient and cost-effective drug development and subsequent disease management. Inflammatory models of respiratory disease combined with sputum biomarkers are important tools in this approach.

Oxygen Therapy in Critical Illness: Friend or Foe? A Review of Oxygen Therapy in Selected Acute Illnesses

In recent years there has been a gradual shift away from using uncontrolled high concentrations of inspired oxygen in some acute illnesses. Oxygen is perhaps the most frequently used drug in medicine, and understanding the balance of benefits and harms is essential knowledge for all anaesthetists and intensivists. While current teaching and practice emphasise avoiding hypoxaemia over concerns about hyperoxaemia, it may transpire that oxygen excess is more harmful than previously thought. As with many interventions in intensive care medicine, striving to achieve physiological normality may sometimes do more harm than good, and tolerance of abnormal values may on occasion be in patients' best interests. Incorporating Single Best Answers (see page 197: answers on page 237).

Melatonin inhibits MUC5AC production via suppression of MAPK signaling in human airway epithelial cells

Mucus acts as a primary defense system in the airway against various stimuli. However, excess mucus production causes a reduction in lung function via limitation of the airflow in the airway of patients suffering from asthma or chronic obstructive pulmonary disease (COPD). In this study, we evaluated the effects of melatonin on the production of MUC5AC, a major constituent of the mucin that is secreted from the airway, using epidermal growth factor (EGF)-stimulated NCI-H292 cells, a human mucoepidermoid carcinoma cell line, and an ovalbumin (OVA)-induced asthma murine model. Melatonin treatment significantly reduced the mRNA and protein levels of MUC5AC and reduced interleukin (IL)-6 production in EGF-stimulated H292 cells. Melatonin markedly decreased the phosphorylation of MAPKs, including ERK1/2, JNK, and p-38, induced by EGF stimulation. These findings were consistent with the results using MAPK inhibitors. Particularly, co-treatment with melatonin and a MAPK inhibitor more effectively suppressed MAPK phosphorylation than treatment with a MAPK inhibitor alone, which resulted in a reduction in MUC5AC expression. In the asthma murine model, melatonin-treated mice exhibited a marked reduction in MUC5AC expression in the airway compared with the OVA-induced mice. These reductions were accompanied by reductions in proinflammatory cytokine production and inflammatory cell infiltration. Collectively, these findings indicate that melatonin effectively inhibits MUC5AC expression. These effects may be closely associated with the inhibition of MAPK phosphorylation. Furthermore, our study suggests that melatonin could represent a potential therapeutic for chronic airway diseases, such as asthma and COPD.

Effects of antioxidant supplements and nutrients on patients with asthma and allergies

Asthma and allergic diseases have become a worldwide public health concern because of their increased prevalence. Despite decades of research on risk factors, the causes of these disorders are poorly understood. They are thought to develop through complex interactions between genetic and environmental factors. Because pulmonary and systemic oxidative stress increase inflammatory responses relevant to asthma and allergy, dietary or vitamin supplementation with antioxidants (a broad and varied category) has been proposed as an approach to reducing asthma incidence or morbidity. Meta-analyses of observational epidemiologic studies of variable methodological quality suggest associations of relatively low dietary intake of antioxidants and higher asthma and allergy prevalence. However, there have been few longitudinal studies of maternal or child dietary or vitamin/supplement antioxidant intake and asthma/allergy development. Moreover, there are no clinical trial data to support the use of dietary antioxidants or supplements to prevent asthma or allergy. A few small clinical trials suggest that specific antioxidants from diet or vitamin supplements might improve asthma control or lung function in asthmatic children or adults. Studies suggest that responses to antioxidants might be modified by life stage, genetic susceptibility, and environmental sources of oxidative stress. Large trials of antioxidant vitamin supplementation to prevent cancer suggest an increase in overall mortality with antioxidant vitamin supplementation, at least in populations with sufficient dietary antioxidant intake. This cautionary experience suggests that future trials to assess whether antioxidants reduce asthma incidence or improve asthma control should focus on supplementation of dietary sources of antioxidants. The potential benefits and risks of trials of vitamin supplements might be considered in special situations in which vulnerable populations have marked deficiency in dietary antioxidants, poor access to dietary antioxidants, and high exposure to environmental sources of oxidants.

Ambroxol inhibits neutrophil respiratory burst activated by alpha chain integrin adhesion

The purpose of the present study was to investigate the possible anti-oxidant effect(s) of Ambroxol on neutrophils activated by ligand-binding of the drug with membrane-associated adhesion integrin CD11a and to estimate dose-response changes in oxygen free radical production. The amount of free radical production by anti-CD11a- and anti-CD4-coated neutrophils stimulated with N-formyl-methionyl-leucyl-phenylalanine (FMLP) and challenged with increasing concentration of Ambroxol, was evaluated within a time frame of 90 minutes. A significant dose-dependent effect response of Ambroxol on O2‾ production by cells coated with anti-CD11a antibody was observed. This preliminary study opens a new perspective on the therapeutic role of Ambroxol as an antioxidant drug and for its potential use in controlling oxidative stress, particularly in leukocyte-dependent inflammation.

Sphingosine 1-phosphate (S1P) induced interleukin-8 (IL-8) release is mediated by S1P receptor 2 and nuclear factor κB in BEAS-2B cells

The airway epithelium may release pro-inflammatory cytokines and chemokines in the asthmatic airway. Sphingosine 1-phosphate (S1P) is a bioactive lipid, increased in the airways of asthmatics, that may trigger the release of the potent neutrophil chemoattractant Interleukin-8 (IL-8) by epithelial cells. S1P is a ligand for 5 G protein-coupled receptors, S1PR1-5. We wished to explore the mechanisms of S1P induced IL-8 secretion with regard to the receptor(s) and downstream signaling events involved. Our results indicate that S1P induced IL-8 release is mediated by S1PR2 and the transcription factor NF-κB. Since the Epidermal Growth Factor Receptor (EGFR) and reactive oxygen species (ROS) have been implicated in IL-8 release in response to activation of other G protein-coupled receptors, we examined their importance in S1P induced IL-8 release and established that they are not involved. This study reveals S1PR2 and NF-κB as potential therapeutic targets in neutrophilic airway diseases such as severe asthma.

What makes a difference in exercise-induced bronchoconstriction: an 8 year retrospective analysis

Background

Exercise-induced bronchoconstriction (EIB) was recently classified into EIB alone and EIB with asthma, based on the presence of concurrent asthma.

Objective

Differences between EIB alone and EIB with asthma have not been fully described.

Methods

We retrospectively reviewed who visited an allergy clinic for respiratory symptoms after exercise and underwent exercise bronchial provocation testing. More than a 15% decrease of forced expiratory volume in 1 second (FEV1) from baseline to the end of a 6 min free-running challenge test was interpreted as positive EIB.

Results

EIB was observed in 66.9% of the study subjects (89/133). EIB-positive subjects showed higher positivity to methacholine provocation testing (61.4% vs. 18.9%, p<0.001) compared with EIB-negative subjects. In addition, sputum eosinophilia was more frequently observed in EIB-positive subjects than in EIB-negative subjects (56% vs. 23.5%, p = 0.037). The temperature and relative humidity on exercise test day were significantly related with the EIB-positive rate. Positive EIB status was correlated with both temperature (p = 0.001) and relative humidity (p = 0.038) in the methacholine-negative EIB group while such a correlation was not observed in the methacholine-positive EIB group. In the methacholine-positive EIB group the time to reach a 15% decrease in FEV1 during exercise was significantly shorter than that in the methacholine-negative EIB group (3.2±0.7 min vs. 8.6±1.6 min, p = 0.004).

Conclusions

EIB alone may be a distinct clinical entity from EIB with asthma. Conditions such as temperature and humidity should be considered when performing exercise tests, especially in subjects with EIB alone.

Respiratory Viral Infections and Subversion of Cellular Antioxidant Defenses

Reactive oxygen species (ROS) formation is part of normal cellular aerobic metabolism, due to respiration and oxidation of nutrients in order to generate energy. Low levels of ROS are involved in cellular signaling and are well controlled by the cellular antioxidant defense system. Elevated levels of ROS generation due to pollutants, toxins and radiation exposure, as well as infections, are associated with oxidative stress causing cellular damage. Several respiratory viruses, including respiratory syncytial virus (RSV), human metapneumovirus (hMPV) and influenza, induce increased ROS formation, both intracellularly and as a result of increased inflammatory cell recruitment at the site of infection. They also reduce antioxidant enzyme (AOE) levels and/or activity, leading to unbalanced oxidative-antioxidant status and subsequent oxidative cell damage. Expression of several AOE is controlled by the activation of the nuclear transcription factor NF-E2-related factor 2 (Nrf2), through binding to the antioxidant responsive element (ARE) present in the AOE gene promoters. While exposure to several pro-oxidant stimuli usually leads to Nrf2 activation and upregulation of AOE expression, respiratory viral infections are associated with inhibition of AOE expression/activity, which in the case of RSV and hMPV is associated with reduced Nrf2 nuclear localization, decreased cellular levels and reduced ARE-dependent gene transcription. Therefore, administration of antioxidant mimetics or Nrf2 inducers represents potential viable therapeutic approaches to viral-induced diseases, such as respiratory infections and other infections associated with decreased cellular antioxidant capacity.

Effects of N-acetylcysteine in ozone-induced chronic obstructive pulmonary disease model

Introduction

Chronic exposure to high levels of ozone induces emphysema and chronic inflammation in mice. We determined the recovery from ozone-induced injury and whether an antioxidant, N-acetylcysteine (NAC), could prevent or reverse the lung damage.

Methods

Mice were exposed to ozone (2.5 ppm, 3 hours/12 exposures, over 6 weeks) and studied 24 hours (24h) or 6 weeks (6W) later. Nac (100 mg/kg, intraperitoneally) was administered either before each exposure (preventive) or after completion of exposure (therapeutic) for 6 weeks.

Results

After ozone exposure, there was an increase in functional residual capacity, total lung volume, and lung compliance, and a reduction in the ratio of forced expiratory volume at 25 and 50 milliseconds to forced vital capacity (FEV₂₅/FVC, FEV₅₀/FVC). Mean linear intercept (L_m) and airway hyperresponsiveness (AHR) to acetylcholine increased, and remained unchanged at 6W after cessation of exposure. Preventive NAC reduced the number of BAL macrophages and airway smooth muscle (ASM) mass. Therapeutic NAC reversed AHR, and reduced ASM mass and apoptotic cells.

Conclusion

Emphysema and lung function changes were irreversible up to 6W after cessation of ozone exposure, and were not reversed by NAC. The beneficial effects of therapeutic NAC may be restricted to the ASM.

Lung cancer: what are the links with oxidative stress, physical activity and nutrition

Oxidative stress appears to play an essential role as a secondary messenger in the normal regulation of a variety of physiological processes, such as apoptosis, survival, and proliferative signaling pathways. Oxidative stress also plays important roles in the pathogenesis of many diseases, including aging, degenerative disease, and cancer. Among cancers, lung cancer is the leading cause of cancer in the Western world. Lung cancer is the commonest fatal cancer whose risk is dependent on the number of cigarettes smoked per day as well as the number of years smoking, some components of cigarette smoke inducing oxidative stress by transmitting or generating oxidative stress. It can be subdivided into two broad categories, small cell lung cancer and non-small-cell lung cancer, the latter is the most common type. Distinct measures of primary and secondary prevention have been investigated to reduce the risk of morbidity and mortality caused by lung cancer. Among them, it seems that physical activity and nutrition have some beneficial effects. However, physical activity can have different influences on carcinogenesis, depending on energy supply, strength and frequency of exercise loads as well as the degree of exercise-mediated oxidative stress. Micronutrient supplementation seems to have a positive impact in lung surgery, particularly as an antioxidant, even if the role of micronutrients in lung cancer remains controversial. The purpose of this review is to examine lung cancer in relation to oxidative stress, physical activity, and nutrition.

Effects of electroacupuncture at Zusanli (ST36) on inflammatory cytokines in a rat model of smoke-induced chronic obstructive pulmonary disease

OBJECTIVE

Improvement in lung function was reported after acupuncture treatment of chronic obstructive pulmonary disease (COPD), but little is known about the underlying mechanisms. Because an immune response imbalance could be seen in COPD, we hypothesize that electroacupuncture (EA) may play a role in regulating inflammatory cytokines and contribute to lung protection in a rat model of smoke-induced COPD.

METHODS

A COPD model using male Sprague-Dawley rats exposed to cigarette smoke was established. The rats were randomly divided into four groups (control, sham, COPD, and COPD plus EA), and COPD model was evaluated by measuring pulmonary pathological changes and lung function. EA was applied to the acupuncture point Zusanli (ST36) for 30 min/d for 14 d in sham and COPD rats. Bronchoalveolar lavage fluid (BALF) was used to measure levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and malonaldehyde (MDA).

RESULTS

Compared with the control rats, COPD rats had significant changes in lung resistance (RL) and lung compliance (CL) (both P<0.01), bronchi and bronchiole airway obstruction (P<0.01), and levels of MDA, TNF-α, and IL-1β (P<0.01). There were no significant differences between the control and the sham groups. Compared with the COPD rats, the COPD plus EA rats had decreased RL and increased CL (both P<0.05), and reduced bronchi and bronchiole airway obstruction (P<0.05, P<0.01, respectively), while levels of TNF-α, IL-1β, and MDA in BALF were lowered (P<0.05 and P<0.01, respectively). However, TNF-α and IL-1β levels of the EA group rats remained higher than those of the control group (P<0.05).

CONCLUSION

EA at ST36 can reduce lung injury in a COPD rat model, and beneficial effects may be related to down-regulation of inflammatory cytokines. The anti-inflammatory and antioxidant effects may prolong the clinical benefit of EA.

Environment and asthma in adults

The present review addresses recent advances and especially challenging aspects regarding the role of environmental risk factors in adult-onset asthma, for which the causes are poorly established. In the first part of the review, we discuss aspects regarding some environmental risk factors for adult-onset asthma: air pollution, occupational exposures with a focus on an emerging risk represented by exposure to cleaning agents (both at home and in the workplace), and lifestyle and nutrition. The second part is focused on perspectives and challenges, regarding relevant topics on which research is needed to improve the understanding of the role of environmental factors in asthma. Aspects of exposure assessment, the complexity of multiple exposures, the interrelationships of the environment with behavioral characteristics and the importance of studying biological markers and gene-environment interactions to identify the role of the environment in asthma are discussed. We conclude that environmental and lifestyle exposures play an important role in asthma or related phenotypes. The changes in lifestyle and the environment in recent decades have modified the specific risk factors in asthma even for well-recognized risks such as occupational exposures. To better understand the role of the environment in asthma, the use of objective (quantitative measurement of exposures) or modern tools (bar code, GPS) and the development of multidisciplinary collaboration would be very promising. A better understanding of the complex interrelationships between socio-economic, nutritional, lifestyle and environmental conditions might help to study their joint and independent roles in asthma.

Age-related increases in ozone-induced injury and altered pulmonary mechanics in mice with progressive lung inflammation

In these studies we determined whether progressive pulmonary inflammation associated with aging in surfactant protein D (Sftpd)-/- mice leads to an exacerbated response to ozone. In Sftpd-/- mice, but not wild-type (WT) mice, age-related increases in numbers of enlarged vacuolated macrophages were observed in the lung, along with alveolar wall rupture, type 2 cell hyperplasia, and increased bronchoalveolar lavage protein and cell content. Numbers of heme oxygenase+ macrophages also increased with age in Sftpd-/- mice, together with classically (iNOS+) and alternatively (mannose receptor+, YM-1+, or galectin-3+) activated macrophages. In both WT and Sftpd-/- mice, increasing age from 8 to 27 wk was associated with reduced lung stiffness, as reflected by decreases in resistance and elastance spectra; however, this response was reversed in 80-wk-old Sftpd-/- mice. Ozone exposure (0.8 ppm, 3 h) caused increases in lung pathology, alveolar epithelial barrier dysfunction, and numbers of iNOS+ macrophages in 8- and 27-wk-old Sftpd-/-, but not WT mice at 72 h postexposure. Conversely, increases in alternatively activated macrophages were observed in 8-wk-old WT mice following ozone exposure, but not in Sftpd-/- mice. Ozone also caused alterations in both airway and tissue mechanics in Sftpd-/- mice at 8 and 27 wk, but not at 80 wk. These data demonstrate that mild to moderate pulmonary inflammation results in increased sensitivity to ozone; however, in senescent mice, these responses are overwhelmed by the larger effects of age-related increases in baseline inflammation and lung injury.

Transient early wheeze and lung function in early childhood associated with chronic obstructive pulmonary disease genes

BACKGROUND

It has been hypothesized that a disturbed early lung development underlies the susceptibility to chronic obstructive pulmonary disease (COPD). Little is known about whether subjects genetically predisposed to COPD show their first symptoms or reduced lung function in childhood.

OBJECTIVE

We investigated whether replicated genes for COPD associate with transient early wheeze (TEW) and lung function levels in 6- to 8-year-old children and whether cigarette smoke exposure in utero and after birth (environmental tobacco smoke [ETS]) modifies these effects.

METHODS

The association of COPD-related genotypes of 20 single nucleotide polymorphisms in 15 genes with TEW, FEV1, forced vital capacity (FVC), and FEV1/FVC ratio was studied in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort (n = 1996) and replicated in the Child, parents and health: lifestyle and genetic constitution (KOALA) and Avon Longitudinal Study of Parents and Children (ALSPAC) cohorts.

RESULTS

AGER showed replicated association with FEV1/FVC ratio. TNS1 associated with more TEW in PIAMA and lower FEV1 in ALSPAC. TNS1 interacted with ETS in PIAMA, showing lower FEV1 in exposed children. HHIP rs1828591 interacted with cigarette smoke exposure in utero in PIAMA and with ETS in ALSPAC, with lower lung function in nonexposed children. SERPINE2, FAM13A, and MMP12 associated with higher FEV1 and FVC, and SERPINE2, HHIP, and TGFB1 interacted with cigarette smoke exposure in utero in PIAMA only, showing adverse effects of exposure on FEV1 being limited to children with genotypes conferring the lowest risk of COPD.

CONCLUSION

Our findings indicate relevant involvement of at least 3 COPD genes in lung development and lung growth by demonstrating associations pointing toward reduced airway caliber in early childhood. Furthermore, our results suggest that COPD genes are involved in the infant's lung response to smoke exposure in utero and in early life.

Oxidative and antioxidative status of children with acute bronchiolitis

OBJECTIVE

Oxidative stress has been shown to contribute to the pathogenesis of acute and chronic lung inflammatory diseases. This article aimed to evaluate the oxidant/antioxidant status of children with acute bronchiolitis through the measurement of plasma total antioxidant capacity, total oxidant status, and oxidative stress index.

METHODS

Children with acute bronchiolitis admitted to the pediatric emergency department of a university hospital between January and April of 2012 were compared with age-matched healthy controls. Patients with acute bronchiolitis were classified as mild and moderate bronchiolitis. Oxidative and antioxidative status were assessed by measurement of plasma total antioxidant capacity, total oxidant status, and oxidative stress index.

RESULTS

Thirty-one children with acute bronchiolitis aged between 3 months and 2 years, and 39 healthy children were included. Total oxidative status (TOS) was higher in patients with acute bronchiolitis than the control group (5.16±1.99 μmol H2O2 versus 3.78±1.78 μmol H2O2 [p=0.004]). Total antioxidant capacity (TAC) was lower in children with bronchiolitis than the control group (2.51±0.37 μmol Trolox eqv/L versus 2.75±0.39 μmol Trolox eqv/L [p=0.013]). Patients with moderate bronchiolitis presented higher TOS levels than those with mild bronchiolitis and the control group (p=0.03, p<0.001, respectively). Patients with moderate bronchiolitis had higher oxidative stress index levels than the control group (p=0.015). Oxygen saturation level of bronchiolitis patients was inversely correlated with TOS (r=-0.476, p<0.05).

CONCLUSION

The balance between oxidant and antioxidant systems is disrupted in children with moderate bronchiolitis, which indicates that this stress factor may have a role in the pathogenesis of the disease.

DASH for asthma: a pilot study of the DASH diet in not-well-controlled adult asthma

This pilot study aims to provide effect size confidence intervals, clinical trial and intervention feasibility data, and procedural materials for a full-scale randomized controlled trial that will determine the efficacy of Dietary Approaches to Stop Hypertension (DASH) as adjunct therapy to standard care for adults with uncontrolled asthma. The DASH diet encompasses foods (e.g., fresh fruit, vegetables, and nuts) and antioxidant nutrients (e.g., vitamins A, C, E, and zinc) with potential benefits for persons with asthma, but it is unknown whether the whole diet is beneficial. Participants (n = 90) will be randomized to receive usual care alone or combined with a DASH intervention consisting of 8 group and 3 individual sessions during the first 3 months, followed by at least monthly phone consultations for another 3 months. Follow-up assessments will occur at 3 and 6 months. The primary outcome measure is the 7-item Juniper Asthma Control Questionnaire, a validated composite measure of daytime and nocturnal symptoms, activity limitations, rescue medication use, and percentage predicted forced expiratory volume in 1 second. We will explore changes in inflammatory markers important to asthma pathophysiology (e.g., fractional exhaled nitric oxide) and their potential to mediate the intervention effect on disease control. We will also conduct pre-specified subgroup analyses by genotype (e.g., polymorphisms on the glutathione S transferase gene) and phenotype (e.g., atopy, obesity). By evaluating a dietary pattern approach to improving asthma control, this study could advance the evidence base for refining clinical guidelines and public health recommendations regarding the role of dietary modifications in asthma management.

Air pollution interacts with past episodes of bronchiolitis in the development of asthma

BACKGROUND

Exposure to ambient air pollution and bronchiolitis are risk factors for asthma. The aim of this study was to investigate the effect of air pollution on the development of asthma in children with past episodes of bronchiolitis.

METHODS

A prospective 2-year follow-up survey consisting of parental responses to the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire, and allergy evaluations were conducted in 1743 children with a mean age of 6.8 years. Recent 5-year exposure to air pollution was estimated using a geographic information system.

RESULTS

Higher exposure to ozone was associated with airway hyper-responsiveness (PC20  ≤ 16 mg/ml) at enrollment (odds ratio [OR] = 1.60, 95% CI [confidence interval] = 1.13-2.27) and with new episodes of wheezing during the 2-year period (OR = 1.92, 95% CI = 0.96-3.83). Past episodes of bronchiolitis were associated with both current wheezing and physician-diagnosed asthma. When the two factors were combined, the prevalence of bronchial hyper-reactivity (OR = 2.96, 95% CI = 1.41-6.24) and new wheezing (OR = 4.17, 95% CI = 0.89-19.66) as well as current wheezing and physician-diagnosed asthma was even greater (P for trend <0.05 for all). In children with both risk factors, lung function was significantly decreased, with atopic children being particularly vulnerable.

CONCLUSION

In children, the interaction between air pollution and past episodes of bronchiolitis resulted in a greater prevalence of asthma and pointed to an association with bronchial hyper-reactivity and decreased lung function. These results suggest mechanisms underlying the development of asthma.

Preventive effect of N-acetylcysteine in a mouse model of steroid resistant acute exacerbation of asthma

Oxidative stress appears to have an important role in glucocorticoid insensitivity, as a crucial problem in asthma therapy. We studied the preventive effect of antioxidant N-acetylcysteine (NAC) on the airway hyper-responsiveness (AHR) and the accumulation of inflammatory cells in the airways in an animal model of steroid resistant acute exacerbation of asthma. Systemically sensitized Balb/C mice were exposed to Ovalbumin aerosol on days 13, 14, 15 and 16, followed by intratracheal lipopolysaccharide (LPS) to induce acute exacerbation. NAC (intraperitoneal, 320 mg/kg 30 min before and 12 hours after each challenge) reduced hyper-responsiveness with/out dexamethasone. LPS application caused neutrophilia in bronchoalveolar lavage fluid (BALF) and eosinophil count was higher than respective control in BALF as well as neutrophils after dexamethasone treatment. NAC significantly decreased neutrophil and eosinophil count in BALF as well as inflammatory cytokines (IL-13 and IL-5).We concluded that addition of NAC to asthma therapy has beneficial preventive effects in an animal model of steroid resistant acute exacerbation of asthma.

Oxidative/Nitrosative stress and the pathobiology of chronic obstructive pulmonary disease

The understanding of the pathobiology of Chronic Obstructive Pulmonary Disease (COPD) has undergone a major change in the past three decades. The classical 'protease-antiprotease' hypothesis still holds true, nevertheless, the sequence of the biochemical events which lead to the protease/antiprotease imbalance have been unraveled. For instance, tobacco smoke, a primary risk factor for COPD, contains a plethora of reactive Oxygen/Nitrogen Species (ROS/RNS) that serve to initiate the oxidant/antioxidant imbalance in the respiratory tract of chronic smokers, a phenomenon that is amplified if certain other risk factors co-exist (e.g. a genetic deficiency of the major antiproteases, a suboptimal antioxidant defense system, airway hyper responsiveness etc.). The inflammatory response that ensues as a result of the initial occult exogenous oxidative/ nitrosative stress becomes a secondary endogenous source of ROS/RNS. This perpetuates the ongoing lung damage, even though the primary insult may no longer be present (abstinence). Depletion of the pulmonary antioxidants, damage to the local antiprotease protective screen, a decreased immune response, hypersecretion of mucus, superadded infections, oxygen therapy-induced oxidant production, etc. are some of the critical factors which account for the oxidative/ nitrosative stress-mediated pulmonary as well as extrapulmonary features of COPD. In the light of the recent developments, remarkable efforts are being made, either to develop novel therapeutic strategies or to improve the existing ones, which are aimed at treating different aspects of the disease. Thus, it is reasonable to recommend antioxidants as a useful adjunct to the more conventional treatment options, keeping in view the 'oxidant/antioxidant' hypothesis as a unifying theme for the 'protease/antiprotease' theory of COPD.

Monitoring intracellular redox changes in ozone-exposed airway epithelial cells

BACKGROUND

The toxicity of many xenobiotic compounds is believed to involve oxidative injury to cells. Direct assessment of mechanistic events involved in xenobiotic-induced oxidative stress is not easily achievable. Development of genetically encoded probes designed for monitoring intracellular redox changes represents a methodological advance with potential applications in toxicological studies.

OBJECTIVE

We tested the utility of redox-sensitive green fluorescent protein (roGFP)-based redox sensors for monitoring real-time intracellular redox changes induced by xenobiotics in toxicological studies.

METHODS

roGFP2, a reporter of the glutathione redox potential (E(GSH)), was used to monitor EGSH in cultured human airway epithelial cells (BEAS-2B cells) undergoing exposure to 0.15-1.0 ppm ozone (O(3)). Cells were imaged in real time using a custom-built O(3) exposure system coupled to a confocal microscope.

RESULTS

O(3) exposure induced a dose- and time-dependent increase of the cytosolic EGSH. Additional experiments confirmed that roGFP2 is not directly oxidized, but properly equilibrates with the glutathione redox couple: Inhibition of endogenous glutaredoxin 1 (Grx1) disrupted roGFP2 responses to O(3), and a Grx1-roGFP2 fusion protein responded more rapidly to O(3) exposure. Selenite-induced up-regulation of GPx (glutathione peroxidase) expression-enhanced roGFP2 responsiveness to O(3), suggesting that (hydro)peroxides are intermediates linking O(3) exposure to glutathione oxidation.

CONCLUSION

Exposure to O(3) induces a profound increase in the cytosolic E(GSH) of airway epithelial cells that is indicative of an oxidant-dependent impairment of glutathione redox homeostasis. These studies demonstrate the utility of using genetically encoded redox reporters in making reliable assessments of cells undergoing exposure to xenobiotics with strong oxidizing properties.

Respiratory syncytial virus infection: mechanisms of redox control and novel therapeutic opportunities

Respiratory syncytial virus (RSV) is one of the most important causes of upper and lower respiratory tract infections in infants and young children, for which no effective treatment is currently available. Although the mechanisms of RSV-induced airway disease remain incompletely defined, the lung inflammatory response is thought to play a central pathogenetic role. In the past few years, we and others have provided increasing evidence of a role of reactive oxygen species (ROS) as important regulators of RSV-induced cellular signaling leading to the expression of key proinflammatory mediators, such as cytokines and chemokines. In addition, RSV-induced oxidative stress, which results from an imbalance between ROS production and airway antioxidant defenses, due to a widespread inhibition of antioxidant enzyme expression, is likely to play a fundamental role in the pathogenesis of RSV-associated lung inflammatory disease, as demonstrated by a significant increase in markers of oxidative injury, which correlate with the severity of clinical illness, in children with RSV infection. Modulation of ROS production and oxidative stress therefore represents a potential novel pharmacological approach to ameliorate RSV-induced lung inflammation and its long-term consequences.

Temperature, nitrogen dioxide, circulating respiratory viruses and acute upper respiratory infections among children in Taipei, Taiwan: a population-based study

OBJECTIVE

This study investigated whether outpatient visits of acute upper respiratory infections for children aged less than 15 years are associated with temperature, air pollutants and circulating respiratory viruses in Taipei, Taiwan, from 2003 to 2007.

METHODS

Outpatient records for acute upper respiratory infections (ICD9 CM codes: 460, 462, 463,464, 465.9 and 487) in a randomly selected sample (n=39,766 children in 2005) was used to estimate the cumulative relative risks (RR) associated with average temperature lasting for 8 days (lag 0-7 days), air pollutants (NO2, O3 and PM(2.5)) lasting for 6 days (lag 0-5 days), and virus-specific positive isolation rate lasting for 11 days (lag 0-10 days) using distributed lag non-linear models after controlling for relative humidity, wind speed, day of week, holiday effects and long-term trend.

RESULTS

Average temperature of 33 °C was associated with the lowest risk for outpatient visits of acute upper respiratory infections. Relative to 33 °C, cumulative 8-day RR was highest at 15 °C of ambient average temperature [RR=1.94; 95% confidence interval (CI): 1.78, 2.11]. With the first quartile as reference, cumulative 6-day RRs were 1.25 (95% CI: 1.21, 1.29) for NO2, 1.04 (95% CI: 1.01, 1.06) for O3, and 1.00 (95% CI: 0.98, 1.03) for PM(2.5) at the 95th percentile. Per-standard deviation (SD) increase of virus-specific isolation rate for influenza type A (SD=13.2%), type B (SD=8.76%), and adenoviruses (SD=5.25%) revealed statistical significance for overall 11-day RRs of 1.02 (95% CI: 1.01, 1.03), 1.05 (95% CI: 1.03, 1.06) and 1.04 (95% CI: 1.03, 1.05), respectively.

CONCLUSIONS

Current study suggested a positive association between outpatient visits for acute upper respiratory infections and ambient environment factors, including average temperature, air pollutants, and circulating respiratory viruses.

Hyperoxic acute lung injury

Prolonged breathing of very high F(IO(2)) (F(IO(2)) ≥ 0.9) uniformly causes severe hyperoxic acute lung injury (HALI) and, without a reduction of F(IO(2)), is usually fatal. The severity of HALI is directly proportional to P(O(2)) (particularly above 450 mm Hg, or an F(IO(2)) of 0.6) and exposure duration. Hyperoxia produces extraordinary amounts of reactive O(2) species that overwhelms natural anti-oxidant defenses and destroys cellular structures through several pathways. Genetic predisposition has been shown to play an important role in HALI among animals, and some genetics-based epidemiologic research suggests that this may be true for humans as well. Clinically, the risk of HALI likely occurs when F(IO(2)) exceeds 0.7, and may become problematic when F(IO(2)) exceeds 0.8 for an extended period of time. Both high-stretch mechanical ventilation and hyperoxia potentiate lung injury and may promote pulmonary infection. During the 1960s, confusion regarding the incidence and relevance of HALI largely reflected such issues as the primitive control of F(IO(2)), the absence of PEEP, and the fact that at the time both ALI and ventilator-induced lung injury were unknown. The advent of PEEP and precise control over F(IO(2)), as well as lung-protective ventilation, and other adjunctive therapies for severe hypoxemia, has greatly reduced the risk of HALI for the vast majority of patients requiring mechanical ventilation in the 21st century. However, a subset of patients with very severe ARDS requiring hyperoxic therapy is at substantial risk for developing HALI, therefore justifying the use of such adjunctive therapies.

Ethyl 3',4',5'-trimethoxythionocinnamate modulates NF-κB and Nrf2 transcription factors

Recently, we identified a novel cinnamate analog, ethyl 3',4',5'-trimethoxythionocinnamate (ETMTC) as a potent inhibitor of cell adhesion molecules (CAMs), such as intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin. However, its mechanism of action has not been elucidated so far. Since, nuclear factor-kappa B (NF-κB) is the major transcription factor involved in the regulation of ICAM-1, VCAM-1 and E-selectin expression, we determined the status of NF-κB activation in ETMTC treated human endothelial cells. Here, we demonstrate that ETMTC inhibits TNF-α-induced nuclear translocation and activation of NF-κB by inhibiting phosphorylation and degradation of IκBα. The inhibition of IκBα phosphorylation and degradation by ETMTC was found to be due to its ability to inhibit IκB kinase activity. In addition, oxidative stress is known to regulate NF-κB activation through TNF-α signaling cascade, therefore, we examined the effect of ETMTC on TNF-α-induced reactive oxygen species generation. We observed that ETMTC significantly inhibits TNF-α-induced reactive oxygen species generation in endothelial cells. To further elucidate the anti-oxidant potential of ETMTC, we examined its effect on induction of anti-oxidant genes viz. glutamate-cysteine ligase, modifier subunit (GCLM), heme oxygenase-1 (HO1) and NAD (P)H:quinone oxidoreductase 1 (NQO1) in human bronchial epithelial cells. Interestingly, ETMTC significantly induces the anti-oxidant genes viz. GCLM, HO1 and NQO1 by activating nuclear factor-erythroid 2 p45-related factor 2 (Nrf2). Thus, ETMTC could be useful towards developing potent anti-inflammatory molecules.

DNA damage due to oxidative stress in Chronic Obstructive Pulmonary Disease (COPD)

According to the American Thorasic Society (ATS)/European Respiratory Society (ERS) Statement, chronic obstructive pulmonary disease (COPD) is defined as a preventable and treatable disease with a strong genetic component, characterized by airflow limitation that is not fully reversible, but is usually progressive and associated with an enhanced inflammatory response of the lung to noxious particles or gases. The main features of COPD are chronic inflammation of the airways and progressive destruction of lung parenchyma and alveolar structure. The pathogenesis of COPD is complex due to the interactions of several mechanisms, such as inflammation, proteolytic/antiproteolytic imbalance, oxidative stress, DNA damage, apoptosis, enhanced senescence of the structural cells and defective repair processes. This review focuses on the effects of oxidative DNA damage and the consequent immune responses in COPD. In susceptible individuals, cigarette smoke injures the airway epithelium generating the release of endogenous intracellular molecules or danger-associated molecular patterns from stressed or dying cells. These signals are captured by antigen presenting cells and are transferred to the lymphoid tissue, generating an adaptive immune response and enhancing chronic inflammation.

Relation of oxidant-antioxidant imbalance with disease progression in patients with asthma

CONTEXT:

Asthma is a chronic airway disorder which is associated to the inflammatory cells. Inflammatory and immune cells generate more reactive oxygen species in patients suffering from asthma which leads to tissue injury.

AIMS:

To investigate the role of oxidant-antioxidant imbalance in disease progression of asthmatic patients.

SETTINGS AND DESIGN:

In this study, 130 asthmatic patients and 70 healthy controls were documented.

METHODS:

For this malondialdehyde level, total protein carbonyls, sulfhydryls, activity of superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), total blood glutathione, and total antioxidant capacity (FRAP) were measured.

STATISTICAL ANALYSIS USED:

Analysis of the data was done using unpaired student t test and one-way ANOVA analysis. P < 0.05 was considered significant.

RESULTS:

The present work showed that the systemic levels of MDA (4.19 ± 0.10 nmol/ml, P < 0.001) and protein carbonyls (1.13 ± 0.02 nmol/mg, P < 0.001) were found to be remarkably higher in asthmatic patients while protein sulfhydryls (0.55 ± 0.01 mmol/l, P < 0.05) decreased as compared to controls (2.84 ± 0.12 nmol/ml, 0.79 ± 0.02 nmol/mg and 0.60 ± 0.02 mmol/l, respectively). We also observed decrease in activities of SOD (2047 ± 50.34 U/g Hb, P < 0.05), catalase (4374 ± 67.98 U/g Hb, P < 0.01), and GPx (40.97 ± 1.05 U/g Hb, P < 0.01) in erythrocytes compared to control (2217 ± 60.11 U/g Hb, 4746 ± 89.94 U/g Hb, and 48.37 ± 2.47 U/g Hb, respectively). FRAP level (750.90 ± 21.22 μmol/l, P < 0.05) in plasma was decreased, whereas total blood glutathione increased (0.94 ± 0.02 mmol/l, P < 0.05) as seen in control (840.40 ± 28.39 μmol/l and 0.84 ± 0.04 mmol/l).

CONCLUSIONS:

This work supports and describes the hypothesis that an imbalance between oxidant-antioxidant is associated to the oxidative stress which plays a significant role in severity of the disease.

Gene expression profiling following NRF2 and KEAP1 siRNA knockdown in human lung fibroblasts identifies CCL11/Eotaxin-1 as a novel NRF2 regulated gene

Background

Oxidative Stress contributes to the pathogenesis of many diseases. The NRF2/KEAP1 axis is a key transcriptional regulator of the anti-oxidant response in cells. Nrf2 knockout mice have implicated this pathway in regulating inflammatory airway diseases such as asthma and COPD. To better understand the role the NRF2 pathway has on respiratory disease we have taken a novel approach to define NRF2 dependent gene expression in a relevant lung system.

Methods

Normal human lung fibroblasts were transfected with siRNA specific for NRF2 or KEAP1. Gene expression changes were measured at 30 and 48 hours using a custom Affymetrix Gene array. Changes in Eotaxin-1 gene expression and protein secretion were further measured under various inflammatory conditions with siRNAs and pharmacological tools.

Results

An anti-correlated gene set (inversely regulated by NRF2 and KEAP1 RNAi) that reflects specific NRF2 regulated genes was identified. Gene annotations show that NRF2-mediated oxidative stress response is the most significantly regulated pathway, followed by heme metabolism, metabolism of xenobiotics by Cytochrome P450 and O-glycan biosynthesis. Unexpectedly the key eosinophil chemokine Eotaxin-1/CCL11 was found to be up-regulated when NRF2 was inhibited and down-regulated when KEAP1 was inhibited. This transcriptional regulation leads to modulation of Eotaxin-1 secretion from human lung fibroblasts under basal and inflammatory conditions, and is specific to Eotaxin-1 as NRF2 or KEAP1 knockdown had no effect on the secretion of a set of other chemokines and cytokines. Furthermore, the known NRF2 small molecule activators CDDO and Sulphoraphane can also dose dependently inhibit Eotaxin-1 release from human lung fibroblasts.

Conclusions

These data uncover a previously unknown role for NRF2 in regulating Eotaxin-1 expression and further the mechanistic understanding of this pathway in modulating inflammatory lung disease.

Metformin reduces airway inflammation and remodeling via activation of AMP-activated protein kinase

Recent reports have suggested that metformin has anti-inflammatory and anti-tissue remodeling properties. We investigated the potential effect of metformin on airway inflammation and remodeling in asthma. The effect of metformin treatment on airway inflammation and pivotal characteristics of airway remodeling were examined in a murine model of chronic asthma generated by repetitive challenges with ovalbumin and fungal-associated allergenic protease. To investigate the underlying mechanism of metformin, oxidative stress levels and AMP-activated protein kinase (AMPK) activation were assessed. To further elucidate the role of AMPK, we examined the effect of 5-aminoimidazole-4-carboxamide-1-β-4-ribofuranoside (AICAR) as a specific activator of AMPK and employed AMPKα1-deficient mice as an asthma model. The role of metformin and AMPK in tissue fibrosis was evaluated using a bleomycin-induced acute lung injury model and in vitro experiments with cultured fibroblasts. Metformin suppressed eosinophilic inflammation and significantly reduced peribronchial fibrosis, smooth muscle layer thickness, and mucin secretion. Enhanced AMPK activation and decreased oxidative stress in lungs was found in metformin-treated asthmatic mice. Similar results were observed in the AICAR-treated group. In addition, the enhanced airway inflammation and fibrosis in heterozygous AMPKα1-deficient mice were induced by both allergen and bleomycin challenges. Fibronectin and collagen expression was diminished by metformin through AMPKα1 activation in cultured fibroblasts. Therefore metformin reduced both airway inflammation and remodeling at least partially through the induction of AMPK activation and decreased oxidative stress. These data provide insight into the beneficial role of metformin as a novel therapeutic drug for chronic asthma.

Antioxidant mimetics modulate oxidative stress and cellular signaling in airway epithelial cells infected with respiratory syncytial virus

Respiratory syncytial virus (RSV) is one of the most common causes of bronchiolitis and pneumonia among infants and young children worldwide. In previous investigations, we have shown that RSV infection induces rapid generation of reactive oxygen species (ROS), which modulate viral-induced cellular signaling, and downregulation of antioxidant enzyme (AOE) expression, resulting in oxidative stress in vitro and in vivo, which plays a pathogenetic role in RSV-induced lung disease. In this study, we determined whether pharmacological intervention with synthetic catalytic scavengers could reduce RSV-induced proinflammatory gene expression and oxidative cell damage in an in vitro model of infection. Treatment of airway epithelial cells (AECs) with the salen-manganese complexes EUK-8 or EUK-189, which possess superoxide dismutase, catalase, and glutathione peroxidase activity, strongly reduced RSV-induced ROS formation by increasing cellular AOE enzymatic activity and levels of the lipid peroxidation products F(2)-8-isoprostane and malondialdehyde, which are markers of oxidative stress. Treatment of AECs with AOE mimetics also significantly inhibited RSV-induced cytokine and chemokine secretion and activation of the transcription factors nuclear factor-κB and interferon regulatory factor-3, which orchestrate proinflammatory gene expression. Both EUKs were able to reduce viral replication, when used at high doses. These results suggest that increasing antioxidant cellular capacities can significantly impact RSV-associated oxidative cell damage and cellular signaling and could represent a novel therapeutic approach in modulating virus-induced lung disease.

Air pollution and asthma control in the Epidemiological study on the Genetics and Environment of Asthma

BACKGROUND

The associations between exposure to air pollution and asthma control are not well known. The objective of this study was to assess the association between long-term exposure to NO(2), O(3) and PM(10) and asthma control in the follow-up of the Epidemiological study on the Genetics and Environment of Asthma (EGEA2) (2003-2007).

METHODS

Modelled outdoor NO(2), O(3) and PM(10) estimates were linked to each residential address using the 4 km grid air pollutant surface developed by the French Institute of Environment in 2004. Asthma control was assessed in 481 subjects with current asthma using a multidimensional approach following the 2006-2009 Global Initiative for Asthma guidelines. Multinomial and ordinal logistic regressions were conducted adjusted for sex, age, body mass index, education, smoking and use of inhaled corticosteroids. The association between air pollution and the three domains of asthma control (symptoms, exacerbations and lung function) was assessed. ORs are reported per IQR.

RESULTS

Median concentrations (in micrograms per cubic metre) were 32 (IQR 25-38) for NO(2) (n=465), 46 (41-52) for O(3) and 21 (18-21) for PM(10) (n=481). In total, 44%, 29% and 27% had controlled, partly controlled and uncontrolled asthma, respectively. The ordinal ORs for O(3) and PM(10) with asthma control were 1.69 (95% CI 1.22 to 2.34) and 1.35 (95% CI 1.13 to 1.64), respectively. When including both pollutants in the same model, both associations persisted. Associations were not modified by sex, smoking status, use of inhaled corticosteroids, atopy, season of examination or body mass index. Both pollutants were associated with each of the three main domains of control.

CONCLUSIONS

The results suggest that long-term exposure to PM(10) and O(3) is associated with uncontrolled asthma in adults, defined by symptoms, exacerbations and lung function.

Prolonged injury and altered lung function after ozone inhalation in mice with chronic lung inflammation

Surfactant protein-D (Sftpd) is a pulmonary collectin important in down-regulating macrophage inflammatory responses. In these experiments, we analyzed the effects of chronic macrophage inflammation attributable to loss of Sftpd on the persistence of ozone-induced injury, macrophage activation, and altered functioning in the lung. Wild-type (Sftpd(+/+)) and Sftpd(-/-) mice (aged 8 wk) were exposed to air or ozone (0.8 parts per million, 3 h). Bronchoalveolar lavage (BAL) fluid and tissue were collected 72 hours later. In Sftpd(-/-) mice, but not Sftpd(+/+) mice, increased BAL protein and nitrogen oxides were observed after ozone inhalation, indicating prolonged lung injury and oxidative stress. Increased numbers of macrophages were also present in BAL fluid and in histologic sections from Sftpd(-/-) mice. These cells were enlarged and foamy, suggesting that they were activated. This conclusion was supported by findings of increased BAL chemotactic activity, and increased expression of inducible nitric oxide synthase in lung macrophages. In both Sftpd(+/+) and Sftpd(-/-) mice, inhalation of ozone was associated with functional alterations in the lung. Although these alterations were limited to central airway mechanics in Sftpd(+/+) mice, both central airway and parenchymal mechanics were modified by ozone exposure in Sftpd(-/-) mice. The most notable changes were evident in resistance and elastance spectra and baseline lung function, and in lung responsiveness to changes in positive end-expiratory pressure. These data demonstrate that a loss of Sftpd is associated with prolonged lung injury, oxidative stress, and macrophage accumulation and activation in response to ozone, and with more extensive functional changes consistent with the loss of parenchymal integrity.

Genomics and the respiratory effects of air pollution exposure

Adverse health effects from air pollutants remain important, despite improvement in air quality in the past few decades. The exact mechanisms of lung injury from exposure to air pollutants are not yet fully understood. Studying the genome (e.g. single-nucleotide polymorphisms (SNP) ), epigenome (e.g. methylation of genes), transcriptome (mRNA expression) and microRNAome (microRNA expression) has the potential to improve our understanding of the adverse effects of air pollutants. Genome-wide association studies of SNP have detected SNP associated with respiratory phenotypes; however, to date, only candidate gene studies of air pollution exposure have been performed. Changes in epigenetic processes, such DNA methylation that leads to gene silencing without altering the DNA sequence, occur with air pollutant exposure, especially global and gene-specific methylation changes. Respiratory cell line and animal models demonstrate distinct gene expression signatures in the transcriptome, arising from exposure to particulate matter or ozone. Particulate matter and other environmental toxins alter expression of microRNA, which are short non-coding RNA that regulate gene expression. While it is clearly important to contain rising levels of air pollution, strategies also need to be developed to minimize the damaging effects of air pollutant exposure on the lung, especially for patients with chronic lung disease and for people at risk of future lung disease. Careful study of genomic responses will improve our understanding of mechanisms of lung injury from air pollution and enable future clinical testing of interventions against the toxic effects of air pollutants.

Glutathione-S-transferase M1 regulation of diesel exhaust particle-induced pro-inflammatory mediator expression in normal human bronchial epithelial cells

Background

Diesel exhaust particles (DEP) contribute substantially to ambient particulate matter (PM) air pollution in urban areas. Inhalation of PM has been associated with increased incidence of lung disease in susceptible populations. We have demonstrated that the glutathione S-transferase M1 (GSTM1) null genotype could aggravate DEP-induced airway inflammation in human subjects. Given the critical role airway epithelial cells play in the pathogenesis of airway inflammation, we established the GSTM1 deficiency condition in primary bronchial epithelial cells from human volunteers with GSTM1 sufficient genotype (GSTM1+) using GSTM1 shRNA to determine whether GSTM1 deficiency could exaggerate DEP-induced expression of interleukin-8 (IL-8) and IL-1β proteins. Furthermore, the mechanisms underlying GSTM1 regulation of DEP-induced IL-8 and IL-1β expression were also investigated.

Methods

IL-8 and IL-1β protein levels were measured using enzyme-linked immunosorbent assay. GSTM1 deficiency in primary human bronchial epithelial cells was achieved using lentiviral GSTM1 shRNA particles and verified using real-time polymerase chain reaction and immunoblotting. Intracellular reactive oxygen species (ROS) production was evaluated using flow cytometry. Phosphorylation of protein kinases was detected using immunoblotting.

Results

Exposure of primary human bronchial epithelial cells (GSTM1+) to 25-100 μg/ml DEP for 24 h significantly increased IL-8 and IL-1β protein expression. Knockdown of GSTM1 in these cells further elevated DEP-induced IL-8 and IL-1β expression, implying that GSTM1 deficiency aggravated DEP-induced pro-inflammatory response. DEP stimulation induced the phosphorylation of extracellular signal-regulated kinase (ERK) and Akt, the downstream kinase of phosphoinositide 3-kinase (PI3K), in GSTM1+ bronchial epithelial cells. Pharmacological inhibition of ERK kinase and PI3K activity blocked DEP-induced IL-8 and IL-1β expression. DEP-induced ERK and Akt phosphorylation could be increased by GSTM1 knockdown. In addition, pretreatment of HBEC with the antioxidant N-acetyl cysteine significantly inhibited DEP-induced ERK and Akt phosphorylation, and subsequent IL-8 and IL-1β expression.

Conclusion

GSTM1 regulates DEP-induced IL-8 and IL-1β expression in primary human bronchial epithelial cells by modulation of ROS, ERK and Akt signaling.

Motor vehicle air pollution and asthma in children: a meta-analysis

BACKGROUND

Asthma affects more than 17 million people in the United States;1/3 of these are children. Children are particularly vulnerable to airborne pollution because of their narrower airways and because they generally breathe more air per pound of body weight than adults, increasing their exposure to air pollutants. However, the results from previous studies on the association between motor vehicle emissions and the development of childhood wheeze and asthma are conflicting. Therefore, we conducted a meta-analysis to clarify their potential relationship.

METHODS

MEDLINE, Highwire, and The Cochrane Library databases were searched for relevant studies. Adjusted odds ratio (OR) with corresponding 95% confidence interval (CI) for the association between traffic air pollutants and wheeze or asthma were retrieved from individual studies and pooled to generate summary effect estimates (meta-OR) in STATA 11.1.

RESULTS

Nineteen studies were included in the meta-analysis. Exposure to nitrogen dioxide (meta-OR: 1.05, 95% CI: 1.00-1.11), nitrous oxide (meta-OR: 1.02, 95% CI: 1.00-1.04), and carbon monoxide (meta-OR: 1.06, 95% CI: 1.01-1.12) were positively associated with a higher prevalence of childhood asthma. Exposure to sulfur dioxide (meta-OR: 1.04, 95% CI: 1.01-1.07) was positively associated with a higher prevalence of wheeze in children. Exposure to nitrogen dioxide was positively associated with a higher incidence of childhood asthma (meta-OR: 1.14, 95% CI: 1.06-1.24), and exposures to particulate matter was positively associated with a higher incidence of wheeze in children (meta-OR: 1.05, 95% CI: 1.04-1.07).

CONCLUSIONS

Living or attending schools near high traffic density roads exposes children to higher levels of motor vehicle air pollutants, and increases the incidence and prevalence of childhood asthma and wheeze.

Synergistic protection against hyperoxia-induced lung injury by neutrophils blockade and EC-SOD overexpression

Background

Oxygen may damage the lung directly via generation of reactive oxygen species (ROS) or indirectly via the recruitment of inflammatory cells, especially neutrophils. Overexpression of extracellular superoxide dismutase (EC-SOD) has been shown to protect the lung against hyperoxia in the newborn mouse model. The CXC-chemokine receptor antagonist (Antileukinate) successfully inhibits neutrophil influx into the lung following a variety of pulmonary insults. In this study, we tested the hypothesis that the combined strategy of overexpression of EC-SOD and inhibiting neutrophil influx would reduce the inflammatory response and oxidative stress in the lung after acute hyperoxic exposure more efficiently than either single intervention.

Methods

Neonate transgenic (Tg) (with an extra copy of hEC-SOD) and wild type (WT) were exposed to acute hyperoxia (95% FiO₂ for 7 days) and compared to matched room air groups. Inflammatory markers (myeloperoxidase, albumin, number of inflammatory cells), oxidative markers (8-isoprostane, ratio of reduced/oxidized glutathione), and histopathology were examined in groups exposed to room air or hyperoxia. During the exposure, some mice received a daily intraperitoneal injection of Antileukinate.

Results

Antileukinate-treated Tg mice had significantly decreased pulmonary inflammation and oxidative stress compared to Antileukinate-treated WT mice (p < 0.05) or Antileukinate-non-treated Tg mice (p < 0.05).

Conclusion

Combined strategy of EC-SOD and neutrophil influx blockade may have a therapeutic benefit in protecting the lung against acute hyperoxic injury.

Exhaled breath 8-isoprostane as a marker of asthma severity

INTRODUCTION

Oxidative stress is a non-specific feature of airway inflammation in asthmatics. 8-Isoprostane (8-IP), a prostaglandin-F(2α) isomer, is a relatively new marker of oxidative stress and may be measured in exhaled breath condensate (EBC) of patients with asthma. This research study aimed to evaluate the usefulness of EBC 8-IP as a marker of severity and control of severe adult asthma.

MATERIAL AND METHODS

Twenty-seven severe, never-smoking asthmatics were studied. According to positive or negative reversibility testing, this group was subdivided into reversible and irreversible asthma groups. All participants were observed for 8 weeks during which they completed daily diary observations including day and night symptoms, number of awakenings, peak expiratory flow (PEF) variability, daily rescue medication usage and oral steroids consumption. They attended the clinic 3 times and on these occasions spirometry assessments, EBC collection and asthma control tests (ACT) were done. Two control groups were included: 11 healthy never-smokers and 16 newly diagnosed and never-treated, non-smoking mild asthmatics.

RESULTS

There were no statistically significant differences between severe asthma and healthy control or never-treated asthma groups in concentrations of EBC 8-IP (median and interquartile range: 4.67; 2.50-27.92 vs. 6.93; 2.5-12.98 vs. 3.80; 2.50-10.73, respectively). No correlations were found between EBC 8-IP and asthma control parameters, such as ACT results, night and day symptoms, consumption of rescue medication, percentage of days free of oral steroids, PEF diurnal variation, lung function test results, forced expiratory volume in the 1 s reversibility, and markers of systemic inflammation.

CONCLUSIONS

Our study results suggest that EBC 8-IP measurements are not useful for asthma monitoring.

Sitagliptin exerts anti-inflammatory and anti-allergic effects in ovalbumin-induced murine model of allergic airway disease

Sitagliptin, a new oral glucose lowering medication, is used for treatment of type 2 diabetes mellitus. The anti-inflammatory property of sitagliptin is reported, yet no studies have been done on asthma. In the present study, the effect of sitagliptin on allergic asthma was investigated using ovalbumin (OVA)-induced asthma model in mice. Swiss male albino mice sensitized and challenged to ovalbumin were treated with sitagliptin (8 mg/kg administered orally twice a day). Drug treatment was done on each day from days 16 to 23, 1 h before the challenge on the days of challenge. Sitagliptin treatment markedly decreased inflammatory cell accumulation in bronchoalveolar lavage (BAL) fluid and in the lungs, as revealed by histopathological examination. Furthermore, the levels of interleukin (IL)-13 in BAL fluid, total and OVA specific immunoglobulins (Ig)-E in serum, were significantly reduced as compared to the OVA group. In addition, sitagliptin significantly increased superoxidase dismutase (SOD) and reduced glutathione (GSH) activities with significant decrease in malondialdehyde (MDA) content in the lung. Importantly, sitagliptin decreased mRNA expression of the inflammatory cytokines tumor necrosis factor-α (TNF-α) and transforming growth factor-β(1) (TGF-β(1)) in lung tissues as compared to the OVA group. Moreover, nitric oxide content as well as the mRNA expression of inducible nitric oxide synthase (iNOS) was remarkably decreased by sitagliptin treatment. Sitagliptin attenuates the allergic airway inflammation suggesting that sitagliptin may have applications in the treatment of bronchial asthma.

Ambient air pollution and allergic diseases in children

The prevalence of allergic diseases has increased worldwide, a phenomenon that can be largely attributed to environmental effects. Among environmental factors, air pollution due to traffic is thought to be a major threat to childhood health. Residing near busy roadways is associated with increased asthma hospitalization, decreased lung function, and increased prevalence and severity of wheezing and allergic rhinitis. Recently, prospective cohort studies using more accurate measurements of individual exposure to air pollution have been conducted and have provided definitive evidence of the impact of air pollution on allergic diseases. Particulate matter and ground-level ozone are the most frequent air pollutants that cause harmful effects, and the mechanisms underlying these effects may be related to oxidative stress. The reactive oxidative species produced in response to air pollutants can overwhelm the redox system and damage the cell wall, lipids, proteins, and DNA, leading to airway inflammation and hyper-reactivity. Pollutants may also cause harmful effects via epigenetic mechanisms, which control the expression of genes without changing the DNA sequence itself. These mechanisms are likely to be a target for the prevention of allergies. Further studies are necessary to identify children at risk and understand how these mechanisms regulate gene-environment interactions. This review provides an update of the current understanding on the impact of air pollution on allergic diseases in children and facilitates the integration of issues regarding air pollution and allergies into pediatric practices, with the goal of improving pediatric health.

Classical and alternative macrophage activation in the lung following ozone-induced oxidative stress

Ozone is a pulmonary irritant known to cause oxidative stress, inflammation and tissue injury. Evidence suggests that macrophages play a role in the pathogenic response; however, their contribution depends on the mediators they encounter in the lung which dictate their function. In these studies we analyzed the effects of ozone-induced oxidative stress on the phenotype of alveolar macrophages (AM). Exposure of rats to ozone (2 ppm, 3h) resulted in increased expression of 8-hydroxy-2'-deoxyguanosine (8-OHdG), as well as heme oxygenase-1 (HO-1) in AM. Whereas 8-OHdG was maximum at 24h, expression of HO-1 was biphasic increasing after 3h and 48-72 h. Cleaved caspase-9 and beclin-1, markers of apoptosis and autophagy, were also induced in AM 24h post-ozone. This was associated with increased bronchoalveolar lavage protein and cells, as well as matrix metalloproteinase (MMP)-2 and MMP-9, demonstrating alveolar epithelial injury. Ozone intoxication resulted in biphasic activation of the transcription factor, NFκB. This correlated with expression of monocyte chemotactic protein-1, inducible nitric oxide synthase and cyclooxygenase-2, markers of proinflammatory macrophages. Increases in arginase-1, Ym1 and galectin-3 positive anti-inflammatory/wound repair macrophages were also observed in the lung after ozone inhalation, beginning at 24h (arginase-1, Ym1), and persisting for 72 h (galectin-3). This was associated with increased expression of pro-surfactant protein-C, a marker of Type II cell proliferation and activation, important steps in wound repair. These data suggest that both proinflammatory/cytotoxic and anti-inflammatory/wound repair macrophages are activated early in the response to ozone-induced oxidative stress and tissue injury.

Inhibition of ROS-induced apoptosis in endothelial cells by nitrone spin traps via induction of phase II enzymes and suppression of mitochondria-dependent pro-apoptotic signaling

Oxidative stress is the main etiological factor behind the pathogenesis of various diseases including inflammation, cancer, cardiovascular and neurodegenerative disorders. Due to the spin trapping abilities and various pharmacological properties of nitrones, their application as therapeutic agent has been gaining attention. Though the antioxidant properties of the nitrones are well known, the mechanism by which they modulate the cellular defense machinery against oxidative stress is not well investigated and requires further elucidation. Here, we have investigated the mechanisms of cytoprotection of the nitrone spin traps against oxidative stress in bovine aortic endothelial cells (BAEC). Cytoprotective properties of both the cyclic nitrone 5,5-dimethyl-pyrroline N-oxide (DMPO) and linear nitrone α-phenyl N-tert-butyl nitrone (PBN) against H₂O₂-induced cytotoxicity were investigated. Preincubation of BAEC with PBN or DMPO resulted in the inhibition of H₂O₂-mediated cytotoxicity and apoptosis. Nitrone-treatment resulted in the induction and restoration of phase II antioxidant enzymes via nuclear translocation of NF-E2-related factor 2 (Nrf-2) in oxidatively-challenged cells. Furthermore, the nitrones were found to inhibit the mitochondrial depolarization and subsequent activation of caspase-3 induced by H₂O₂. Significant down-regulation of the pro-apoptotic proteins p53 and Bax, and up-regulation of the anti-apoptotic proteins Bcl-2 and p-Bad were observed when the cells were preincubated with the nitrones prior to H₂O₂-treatment. It was also observed that Nrf-2 silencing completely abolished the protective effects of nitrones. Hence, these findings suggest that nitrones confer protection to the endothelial cells against oxidative stress by modulating phase II antioxidant enzymes and subsequently inhibiting mitochondria-dependent apoptotic cascade.

Air pollution and epigenetics: effects on SP-A and innate host defence in the lung

An appropriate immune and inflammatory response is key to defend against harmful agents present in the environment, such as pathogens, allergens and inhaled pollutants, including ozone and particulate matter. Air pollution is a serious public health concern worldwide, and cumulative evidence has revealed that air pollutants contribute to epigenetic variation in several genes, and this in turn can contribute to disease susceptibility. Several groups of experts have recently reviewed findings on epigenetics and air pollution [1-6]. Surfactant proteins play a central role in pulmonary host defence by mediating pathogen clearance, modulating allergic responses and facilitating the resolution of lung inflammation. Recent evidence indicates that surfactant proteins are subject to epigenetic regulation under hypoxia and other conditions. Oxidative stress caused by ozone, and exposure to particulate matter have been shown to affect the expression of surfactant protein A (SP-A), an important lung host defence molecule, as well as alter its functions. In this review, we discuss recent findings in the fields of epigenetics and air pollution effects on innate immunity, with the focus on SP-A, and the human SP-A variants in particular. Their function may be differentially affected by pollutants and specifically by ozone-induced oxidative stress, and this in turn may differentially affect susceptibility to lung disease.