Reactive oxidant species in asthma

Novel pyridyl-substituted nitronyl nitroxides as potential antiarrhythmic and hypotensive agents with low toxicity and enhanced stability in aqueous solutions

This study explores the antiarrhythmic and hypotensive potential of pyridyl-substituted nitronyl nitroxides derivatives, uncovering the crucial role of a single carbon moiety of the pyridine cycle alongside radical and charged oxygen centers of the imidazoline fragment. Notably, the introduction of fluorine atoms diminished the antiarrhythmic effect, while the most potent derivatives featured the nitronyl nitroxide pattern positioned at the third site of the pyridine cycle. Gender-dependent responses were observed in lead compounds LCF3 and LMe, with LMe inducing temporary bradycardia and hypotension specifically in female rats, and LCF3 causing significant blood pressure reduction followed by rebound in females compared to milder effects in males. Mechanistic insights point towards β1 adrenoceptor blockade as an underlying mechanism, supported by experiments on isolated rat atria. This research underscores the interplay between structure, cardiovascular effects and gender-specific responses, offering insights for therapeutic strategies for treating free radical-associated cardiovascular disorders.

D-ROMs and PAT Tests Reveal a High Level of Oxidative Stress in Patients with Severe Well-Controlled Asthma, and D-ROMs Are Positively Correlated with R20 Values That Indicate Approximate Central Airway Resistance

BACKGROUND

The derivatives-reactive oxygen metabolites (d-ROMs) and plasma antioxidant capacity (PAT) tests are oxidative indexes. Severe asthma has been related to oxidative stress. We aimed to investigate d-ROMs and PAT values in severely controlled asthmatics and the correlation of these values with lung function.

METHODS

Blood samples were collected from severely controlled asthmatics and centrifuged at 3000 rpm for 10 min. The supernatant was collected. The assays were performed within three hours of collection. The fraction of exhaled nitric oxide (FeNO), impulse oscillometry (IOS), and spirometry were determined. Symptom control was recorded using the asthma control test (ACT).

RESULTS

Approximately 40 patients with severe controlled asthma (75%: women), mean age of 62 ± 12 years, were recruited. Approximately 5% had obstructive spirometry. The IOS revealed airway abnormalities even though the spirometric results were within the normal range, with it being more sensitive than spirometry. The D-ROMs and PAT test values were higher than normal, indicating oxidative stress in severe asthmatics with controlled asthma. D-ROMs were positively correlated with R20 values, indicating central airway resistance.

CONCLUSIONS

The IOS technique revealed an otherwise hidden airway obstruction with spirometry. The D-ROMs and PAT tests revealed a high level of oxidative stress in severe controlled asthmatics. D-ROMs correlate with R20, indicating central airway resistance.

Lower circulating zinc and selenium levels are associated with an increased risk of asthma: evidence from a meta-analysis

OBJECTIVE

Previous studies evaluating the associations of circulating Zn and Se levels with asthma have produced inconsistent results. Therefore, we conducted a meta-analysis to summarize and quantitatively synthesize the evidence from observational research.

DESIGN

Meta-analysis.

SETTING

We searched PubMed, Web of Science and Scopus databases up to May 2019 for relevant available articles. Random-effects model was adopted to estimate the pooled standardized mean difference (SMD) with 95 % CI. Meta-regression analysis and 'leave-one-out' sensitivity analysis were used to assess heterogeneity.

PARTICIPANTS

The meta-analysis focused on general populations.

RESULTS

A total of twenty-six studies for Zn and forty studies for Se were included in the meta-analysis. The overall analyses identified that asthma patients had lower Zn (SMD = -0·40; 95 % CI -0·77, -0·03; I2 = 94·1 %) and Se (SMD = -0·32; 95 % CI -0·48, -0·17; I2 = 90·9 %) levels in serum or plasma compared with healthy controls. After removing the studies that contributed to the heterogeneity, the pooled SMD were -0·26 (95 % CI -0·40, -0·13; I2 = 37·42 %) for Zn and -0·06 (95 % CI -0·13, 0·02; I2 = 43·54 %) for Se.

CONCLUSIONS

Lower circulating Zn and Se levels might be associated with an increased risk of asthma.

NOx in exhaled breath condensate is related to allergic sensitization in young and middle-aged adults

BACKGROUND

Asthma and allergic diseases are heterogeneous. Measurement of biomarkers in exhaled breath condensate (EBC) may help to discriminate between different phenotypes and may assist with clinical prognostication.

OBJECTIVES

We aimed to assess associations between total nitric oxide products (NO_x ) in EBC and different allergic phenotypes and lung function in young and middle-aged adults.

METHODS

Cross-sectional analyses were nested within two Australian longitudinal studies, the Melbourne Atopy Cohort Study (MACS, mean age 17.8 years) and the Tasmanian Longitudinal Health Study (TAHS, mean age 49.4 years). Levels of EBC NO_x were determined by Griess-reaction fluorescent method. Associations were assessed between EBC NO_x and different allergic phenotypes, lung function and airway reactivity.

RESULTS

Atopy, with or without asthma or rhinitis, was associated with increased EBC NO_x levels particularly in individuals with poly-aero-sensitization. These findings were generally consistent across the two age groups. In the older cohort, use of ICS in the previous 12 months masked the association between sensitization and EBC NO_x (OR = 0.64, 95% CI = 0.21-1.96, p for interaction = 0.05).

CONCLUSIONS AND CLINICAL RELEVANCE

In these population-based samples, EBC NO_x was most strongly associated with atopic sensitization, rather than either current asthma or rhinitis, possibly indicating underlying increased airway inflammation associated with atopy. Therefore, EBC NO_x could be a key predictor of atopy in both young and middle-aged adults, regardless of the presence of concomitant asthma or rhinitis.

Serum carotenoid and tocopherol concentrations and risk of asthma in childhood: a nested case-control study

BACKGROUND

The antioxidant hypothesis regarding the risk of asthma in childhood has resulted in inconsistent findings. Some data indicate that the role of antioxidants in childhood asthma risk may have a critical time window of effect, but only a well-designed longitudinal cohort study can clarify this hypothesis.

OBJECTIVE

To study the longitudinal associations between serum carotenoid and tocopherol concentrations during the first 4 years of life and asthma risk by the age of 5 years.

METHODS

Based on a case-control design nested within a Finnish birth cohort, 146 asthma cases were matched to 270 controls on birth time, sex, genetic risk, and birth place. Non-fasting blood samples were collected at the ages of 1, 1.5, 2, 3, and 4 years and serum carotenoids and tocopherols were analysed. Parents reported the presence and age at start of persistent doctor-diagnosed asthma in the child at the age of 5 years. Data analyses were conducted using generalized estimating equations.

RESULTS

We did not find strong associations between serum carotenoids and tocopherols and the risk of asthma based on age-specific and longitudinal analyses. Both lower and higher quarters of α-carotene and γ-tocopherol increased the risk of asthma.

CONCLUSIONS

The current findings do not support the suggestion that the increased prevalence of asthma may be a consequence of decreased intake of antioxidant nutrients. Moreover, we did not confirm any critical time window of impact of antioxidants on asthma risk. Replication of these findings in similar longitudinal settings will strengthen this evidence base.

Mitochondrial Dysfunction in Airway Disease

There is increasing appreciation that mitochondria serve cellular functions beyond oxygen sensing and energy production. Accordingly, it has become important to explore noncanonical roles of mitochondria in normal and pathophysiological processes that influence airway structure and function in the context of diseases such as asthma and COPD. Mitochondria can sense upstream processes such as inflammation, infection, tobacco smoke, and environmental insults important in these diseases and in turn can respond to such stimuli through altered mitochondrial protein expression, structure, and resultant dysfunction. Conversely, mitochondrial dysfunction has downstream influences on cytosolic and mitochondrial calcium regulation, airway contractility, gene and protein housekeeping, responses to oxidative stress, proliferation, apoptosis, fibrosis, and certainly metabolism, which are all key aspects of airway disease pathophysiology. Indeed, mitochondrial dysfunction is thought to play a role even in normal processes such as aging and senescence and in conditions such as obesity, which impact airway diseases. Thus, understanding how mitochondrial structure and function play central roles in airway disease may be critical for the development of novel therapeutic avenues targeting dysfunctional mitochondria. In this case, it is likely that mitochondria of airway epithelium, smooth muscle, and fibroblasts play differential roles, consistent with their contributions to disease biology, underlining the challenge of targeting a ubiquitous cellular element of existential importance. This translational review summarizes the current state of understanding of mitochondrial processes that play a role in airway disease pathophysiology and identifying areas of unmet research need and opportunities for novel therapeutic strategies.

Recombinant human deoxyribonuclease attenuates oxidative stress in a model of eosinophilic pulmonary response in mice

The inflammatory cells infiltrating the airways produce several mediators, such as reactive oxygen species (ROS). ROS and the oxidant-antioxidant imbalance might play an important role in the modulation of airways inflammation. In order to avoid the undesirable effects of ROS, various endogenous antioxidant strategies have evolved, incorporating both enzymatic and non-enzymatic mechanisms. Recombinant human deoxyribonuclease (rhDNase) in clinical studies demonstrated a reduction in sputum viscosity, cleaving extracellular DNA in the airways, and facilitating mucus clearance, but an antioxidant effect was not studied so far. Therefore, we evaluated whether the administration of rhDNase improves oxidative stress in a murine model of asthma. Mice were sensitized by two subcutaneous injections of ovalbumin (OVA), on days 0 and 7, followed by three lung challenges with OVA on days 14, 15, and 16. On days 15 and 16, after 2 h of the challenge with OVA, mice received 1 mg/mL of rhDNase in the lungs. Bronchoalveolar lavage fluid and lung tissue were obtained on day 17, for inflammatory and oxidative stress analysis. We showed that rhDNase did not alter the population of inflammatory cells, such as eosinophil cells, in OVA-treated rhDNase group but significantly improved oxidative stress in lung tissue, by decreasing oxygen reactive species and increasing superoxide dismutase/catalase ratio, glutathione peroxidase activity, and thiol content. Our data provide the first evidence that rhDNase decreases some measures of oxidative stress and antioxidant status in a murine model of asthma, with a potential antioxidant effect to be further studied in human asthma.

Anti-oxidant N-acetylcysteine diminishes diesel exhaust-induced increased airway responsiveness in person with airway hyper-reactivity

BACKGROUND

Inhalation of diesel exhaust (DE) at moderate concentrations causes increased airway responsiveness in asthmatics and increased airway resistance in both healthy and asthmatic subjects, but the effect of baseline airway responsiveness and anti-oxidant supplementation on this dynamic is unknown.

OBJECTIVES

We aimed to determine if changes in airway responsiveness due to DE are attenuated by thiol anti-oxidant supplementation, particularly in those with underlying airway hyper-responsiveness.

METHODS

Participants took N-acetylcysteine (600 mg) or placebo capsules three times daily for 6 days. On the last of these 6 days, participants were exposed for 2 h to either filtered air (FA) or DE (300 μg/m(3) of particulate matter smaller than 2.5 microns). Twenty-six non-smokers were studied under each of three experimental conditions (filtered air with placebo, diesel exhaust with placebo, and diesel exhaust with N-acetylcysteine) using a randomized, double-blind, crossover design, with a 2-week washout between conditions. Methacholine challenge was performed pre-exposure (baseline airway responsiveness) and post-exposure (effect of exposure).

RESULTS

Anti-oxidant supplementation reduced baseline airway responsiveness in hyper-responsive individuals by 20% (p = 0.001). In hyper-responsive individuals, airway responsiveness increased 42% following DE compared with FA (p = 0.03) and this increase was abrogated with anti-oxidant supplementation (diesel exhaust with N-acetylcysteine vs. filtered air with placebo, p = 0.85).

CONCLUSIONS

Anti-oxidant (N-acetylcysteine) supplementation protects against increased airway responsiveness associated with DE inhalation and reduces need for supplement bronchodilators in those with baseline airway hyper-responsiveness. Individuals with variants in genes of oxidative stress metabolism when exposed to DE are protected from increases in airway responsiveness if taking anti-oxidant supplementation.

Antioxidant defense enzyme genes and asthma susceptibility: gender-specific effects and heterogeneity in gene-gene interactions between pathogenetic variants of the disease

Oxidative stress resulting from an increased amount of reactive oxygen species and an imbalance between oxidants and antioxidants plays an important role in the pathogenesis of asthma. The present study tested the hypothesis that genetic susceptibility to allergic and nonallergic variants of asthma is determined by complex interactions between genes encoding antioxidant defense enzymes (ADE). We carried out a comprehensive analysis of the associations between adult asthma and 46 single nucleotide polymorphisms of 34 ADE genes and 12 other candidate genes of asthma in Russian population using set association analysis and multifactor dimensionality reduction approaches. We found for the first time epistatic interactions between ADE genes underlying asthma susceptibility and the genetic heterogeneity between allergic and nonallergic variants of the disease. We identified GSR (glutathione reductase) and PON2 (paraoxonase 2) as novel candidate genes for asthma susceptibility. We observed gender-specific effects of ADE genes on the risk of asthma. The results of the study demonstrate complexity and diversity of interactions between genes involved in oxidative stress underlying susceptibility to allergic and nonallergic asthma.

The beta-2-adrenoreceptor agonists, formoterol and indacaterol, but not salbutamol, effectively suppress the reactivity of human neutrophils in vitro

The clinical relevance of the anti-inflammatory properties of beta-2 agonists remains contentious possibly due to differences in their molecular structures and agonist activities. The current study has compared the effects of 3 different categories of β2-agonists, namely, salbutamol (short-acting), formoterol (long-acting) and indacaterol (ultra-long-acting), at concentrations of 1–1000 nM, with human blood neutrophils in vitro. Neutrophils were activated with either N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP, 1 µM) or platelet-activating factor (PAF, 200 nM) in the absence and presence of the β2-agonists followed by measurement of the generation of reactive oxygen species and leukotriene B4, release of elastase, and expression of the β2-integrin, CR3, using a combination of chemiluminescence, ELISA, colorimetric, and flow cytometric procedures respectively. These were correlated with alterations in the concentrations of intracellular cyclic-AMP and cytosolic Ca²⁺. At the concentrations tested, formoterol and indacaterol caused equivalent, significant (P < 0.05 at 1–10 nM) dose-related inhibition of all of the pro-inflammatory activities tested, while salbutamol was much less effective (P < 0.05 at 100 nM and higher). Suppression of neutrophil reactivity was accompanied by elevations in intracellular cAMP and accelerated clearance of Ca²⁺ from the cytosol of activated neutrophils. These findings demonstrate that β2-agonists vary with respect to their suppressive effects on activated neutrophils.

Coexisting chronic conditions associated with mortality and morbidity in adult patients with asthma

OBJECTIVE

Many asthma patients suffer from chronic conditions other than asthma. We investigated the specific contribution of common comorbidities on mortality and morbidity in adult asthma.

METHODS

In an observational study of adults with incident asthma identified between 1999 and 2003 using National Veterans Affairs and Centers for Medicare and Medicaid Services encounter databases (n = 25 975, follow-up 3.0 ± 1.7 years), association between 13 most prevalent comorbidities (hypertension, ischemic heart disease (IHD), osteoarthritis, rheumatoid arthritis, diabetes, mental disorders, substance/drug abuse, enlarged prostate, depression, cancer, alcoholism, HIV and heart failure) and four conditions previously associated with asthma (sleep apnea, gastroesophageal reflux disease (GERD), rhinitis and sinusitis) and mortality, hospitalizations and asthma exacerbations were assessed using multivariate regression analyses adjusted for other clinically important covariates.

RESULTS

HIV followed by alcoholism and mental disorders among 18-45-years old, and heart failure, diabetes, IHD and cancer among those ≥ 65 years old were associated with an increased risk of all-cause mortality. Many conditions were associated with increased risk for all-cause hospitalizations, but the increased risk was consistent across all ages for mental disorders. For asthma exacerbations, mental disorder followed by substance abuse and IHD were associated with increased risk among those 18-45 years old, and chronic sinusitis, mental disorder and IHD among those ≥ 65-years old. GERD was associated with decreased risk for asthma exacerbation in all ages.

CONCLUSIONS

Many comorbidities are associated with poor outcome in adult asthmatics and their effect differs by age. Mental disorders are associated with increased risk of mortality and morbidity across ages.

Quantification of lipid mediator metabolites in human urine from asthma patients by electrospray ionization mass spectrometry: controlling matrix effects

Eicosanoids (e.g., prostaglandins and leukotrienes) are inflammatory signaling molecules that are metabolized and excreted in urine. The quantification of eicosanoid metabolites in human urine has been demonstrated to provide insight into the inflammatory and oxidative stress status of the individual. However, urine is a complex matrix that can exhibit profound matrix effects for quantification via liquid chromatography coupled to mass spectrometry (LC-MS/MS). This phenomenon can lead to impairment and biasing of results, because the sample background is dependent on the fluid intake and water-salt balance. Herein we describe an analytical methodology to address these limitations via the normalization of extracted urine volume by the ratio of absorbance at 300 nm to an optimized reference material. The platform is composed of 4 LC-MS/MS methods that collectively quantify 26 lipid mediators and their metabolites, with on-column limits of detection between 0.55 and 15 fmol. Prior to optimization, internal standards exhibited strong matrix effects with up to 50% loss of signal. Notably, the accuracy of exact deuterated structural analogues was found to vary based upon the number of incorporated deteurium. The platform was used to analyze urine from 16 atopic asthmatics under allergen provocation, showing increases in metabolites of prostaglandin D2, cysteinyl leukotrienes, and isoprostanes following the challenge. This method presents a functional and reproducible approach to addressing urine-specific matrix effects that can be readily formatted for quantifying large numbers of samples.

Changes in NADPH oxidase mRNA level can be detected in blood at inhaled corticosteroid treated asthmatic children

AIM

Oxidative stress, observed in the asthmatic airways, is not localized only to the bronchial system. It would be a great advantage to monitor the oxidative stress markers from blood especially in childhood asthma following the inflammation. Our aim was to measure the levels of antioxidants and the oxidatively damaged biomolecules. We were also interested in the gene expression alterations of the free radical source gp91(phox) subunit (CYBB) of the NADPH oxidase system, and the antioxidant heme oxygenase-1 (HMOX-1) isoenzyme in the blood. Our findings were also examined in the context of medical treatment.

MAIN METHODS

Oxidative stress parameters via photometric methods, CYBB and HMOX-1 expressions via real-time PCR were measured in 58 asthmatic and 30 healthy children.

KEY FINDINGS

Higher blood thiobarbituric acid reactive substances (TBARS) (p<0.03) and carbonylated protein (p<0.05) levels were found in the asthmatic children than in the controls. The relative expression of CYBB was significantly lower (p<0.05) in patients treated with a low daily dose of inhaled corticosteroid (ICS), than in asthmatics not receiving ICS therapy. Higher ICS doses alone or combined with long acting β2-receptor agonists did not influence the expression significantly. No similar tendency was found as regards to HMOX-1 expression.

SIGNIFICANCE

Elevated levels of damaged lipid (TBARS) and protein (carbonylated) products corroborate the presence of oxidative stress in the blood during bronchial asthma and suggest the presence of chronic oxidative overload. Our findings also suggest that ICS treatment can influence the relative CYBB mRNA expression in circulating leukocytes in a dose dependent manner.

Biomarkers in asthma: a real hope to better manage asthma

Diagnosis and treatment of asthma are currently based on assessment of patient symptoms and physiologic tests of airway reactivity. Research over the past decade has identified an array of biochemical and cellular biomarkers, which reflect the heterogeneous and multiple mechanistic pathways that may lead to asthma. These mechanistic biomarkers offer hope for optimal design of therapies targeting the specific pathways that lead to inflammation. This article provides an overview of blood, urine, and airway biomarkers; summarizes the pathologic pathways that they signify; and begins to describe the utility of biomarkers in the future care of patients with asthma.

Regulation of GPCR-mediated smooth muscle contraction: implications for asthma and pulmonary hypertension

Contractile G-protein-coupled receptors (GPCRs) have emerged as key regulators of smooth muscle contraction, both under healthy and diseased conditions. This brief review will discuss some key topics and novel insights regarding GPCR-mediated airway and vascular smooth muscle contraction as discussed at the 7th International Young Investigators' Symposium on Smooth Muscle (2011, Winnipeg, Manitoba, Canada) and will in particular focus on processes driving Ca(2+)-mobilization and -sensitization.

Glutathione peroxidase inhibitory assay for electrophilic pollutants in diesel exhaust and tobacco smoke

We developed a rapid kinetic bioassay demonstrating the inhibition of glutathione peroxidase 1 (GPx-1) by organic electrophilic pollutants, such as acrolein, crotonaldehyde, and p-benzoquinone, that are frequently found as components of tobacco smoke, diesel exhaust, and other combustion sources. In a complementary approach, we applied a high-resolution proton-transfer reaction time-of-flight mass spectrometer to monitor in real-time the generation of electrophilic volatile carbonyls in cigarette smoke. The new bioassay uses the important antioxidant selenoenzyme GPx-1, immobilized to 96-well microtiter plates, as a probe. The selenocysteine bearing subunits of the enzyme's catalytic site are viewed as cysteine analogues and are vulnerable to electrophilic attack by compounds with conjugated carbonyl systems. The immobilization of GPx-1 to microtiter plate wells enabled facile removal of excess reactive inhibitory compounds after incubation with electrophilic chemicals or aqueous extracts of air samples derived from different sources. The inhibitory response of cigarette smoke and diesel exhaust particle extracts were compared with chemical standards of a group of electrophilic carbonyls and the arylating p-benzoquinone. GPx-1 activity was directly inactivated by millimolar concentrations of highly reactive electrophilic chemicals (including acrolein, glyoxal, methylglyoxal, and p-benzoquinone) and extracts of diesel and cigarette smoke. We conclude that the potential of air pollutant components to generate oxidative stress may be, in part, a result of electrophile-derived covalent modifications of enzymes involved in the cytosolic antioxidant defense.

Oxidative stress in asthma

Asthma is a chronic inflammatory lung disease that results in airflow limitation, hyperreactivity, and airway remodeling. There is strong evidence that an imbalance between the reducing and oxidizing systems favoring a more oxidative state is present in asthma. Endogenous and exogenous reactive oxygen species, such as superoxide anion, hydroxyl radical, hypohalite radical, and hydrogen peroxide, and reactive nitrogen species, such as nitric oxide, peroxynitrite, and nitrite, play a major role in the airway inflammation and are determinants of asthma severity. Asthma is also associated with decreased antioxidant defenses, such as superoxide dismutase, catalase, and glutathione. In this review, we will summarize the current knowledge and discuss the current and future strategies for the modulation of oxidative stress in asthma.

Oxidative status in the lungs associated with tobacco smoke exposure

BACKGROUND

Oxidative stress has a critical role in inflammatory responce against tobacco smoke (TS). Testing exhaled breath condensate (EBC) samples is one of the methods used for assessment of airway inflammation caused by TS. We aimed to investigate oxidative stress in the lungs associated with TS and to evaluate the effect of this stress with pulmonary function tests (PFTs).

METHODS

We included 69 subjects as three groups into the study (Group I; 26 smokers, Group II; 21 passive smokers, Group III; 22 non-smokers without TS exposure). Levels of malondialdehyde (MDA), 8-hydroxydeoxyguanosine (8-OHdG), nitrite/nitrate [index of nitric oxide (NO) production], vitamin C, superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) were measured in EBC samples collected using a condenser and PFTs were performed.

RESULTS

The levels of MDA, 8-OHdG, SOD and GSH-Px were higher in smokers. NO levels gradually increased from Group I to Group III. MDA levels were lower in Group III than Group II. The levels of vitamin C were similar in all groups. We determined negative correlation between 8-OHdG levels and forced expiratory volume in one second (FEV₁), and maximum mean expiratory flow (MMEF), and a positive correlation between SOD levels and FEV₁.

CONCLUSIONS

TS exposure affected the balance between oxidative stress and antioxidant capacity of lungs. Preventing environmental TS exposure might decrease oxidative damage. Increased levels of 8-OHdG and SOD levels could be assessed as an early sign of airway damage.

Modification by antioxidant supplementation of changes in human lung function associated with air pollutant exposure: a systematic review

BACKGROUND

Outdoor air pollution, given its demonstrated negative effects on the respiratory system, is a growing public health concern worldwide, particularly in urban cities. Human exposure to pollutants such as ozone, nitrogen oxides, combustion-related particulate matter and oxides of sulfur is responsible for significant cardiopulmonary morbidity and mortality in both adults and children. Several antioxidants have shown an ability to partially attenuate the negative physiological and functional impacts of air pollutants. This study systematically presents current data on the potential benefits of antioxidant supplementation on lung function outcomes associated with air pollutant exposures in intact humans.

METHODS

Electronic databases (MEDLINE, EMBASE, BIOSIS Previews, Web of Sciences, Environmental Sciences & Pollution Management and TOXNET) were systematically searched for all studies published up to April 2009. Search terms relating to the concepts of respiratory tract diseases, respiratory function tests, air pollution, and antioxidants were used. Data was systematically abstracted from original articles that satisfied selection criteria for inclusion. For inclusion, the studies needed to have evaluated human subjects, given supplemental antioxidants, under conditions of known levels of air pollutants with measured lung function before and after antioxidant administration and/or air pollution exposure. Selected studies were summarized and conclusions presented.

RESULTS

Eight studies investigated the role of antioxidant supplementation on measured lung function outcomes after subject exposure to air pollutants under controlled conditions; 5 of these studies concluded that pollutant-induced airway hyper-responsiveness and diminution in lung function measurements were attenuated by antioxidant supplementation. The remaining five studies took place under ambient (uncontrolled) exposures and unanimously concluded that antioxidant supplementations attenuate the negative effects of urban air pollution on lung function.

CONCLUSIONS

The data evaluating modification of changes in lung function associated with air pollutant exposure by antioxidant supplementation, in intact humans, is limited. Of 13 studies dedicated to this concern, ten demonstrated an attenuation of pollution-associated decrements. There is growing evidence for the benefit of anti-oxidant supplementation in moderating the effects of air pollution on lung function, but more research on human participants is needed to inform this topic.

Simple isatin derivatives as free radical scavengers: Synthesis, biological evaluation and structure-activity relationship

To develop more potent small molecules with enhanced free radical scavenger properties, a series of N-substituted isatin derivatives was synthesized, and the cytoprotective effect on the apoptosis of PC12 cells induced by H₂O₂ was screened. All these compounds were found to be active, and N-ethyl isatin was found with the most potent activity of 69.7% protective effect on PC12 cells. Structure-activity relationship analyses showed the bioactivity of N-alkyl isatins decline as the increasing of the chain of the alkyl group, furthermore odd-even effect was found in the activity, which is interesting for further investigation.

Aldose reductase inhibition prevents metaplasia of airway epithelial cells

BACKGROUND

Goblet cell metaplasia that causes mucus hypersecretion and obstruction in the airway lumen could be life threatening in asthma and chronic obstructive pulmonary disease patients. Inflammatory cytokines such as IL-13 mediate the transformation of airway ciliary epithelial cells to mucin-secreting goblet cells in acute as well as chronic airway inflammatory diseases. However, no effective and specific pharmacologic treatment is currently available. Here, we investigated the mechanisms by which aldose reductase (AR) regulates the mucus cell metaplasia in vitro and in vivo.

METHODOLOGY/FINDINGS

Metaplasia in primary human small airway epithelial cells (SAEC) was induced by a Th2 cytokine, IL-13, without or with AR inhibitor, fidarestat. After 48 h of incubation with IL-13 a large number of SAEC were transformed into goblet cells as determined by periodic acid-schiff (PAS)-staining and immunohistochemistry using antibodies against Mucin5AC. Further, IL-13 significantly increased the expression of Mucin5AC at mRNA and protein levels. These changes were significantly prevented by treatment of the SAEC with AR inhibitor. AR inhibition also decreased IL-13-induced expression of Muc5AC, Muc5B, and SPDEF, and phosphorylation of JAK-1, ERK1/2 and STAT-6. In a mouse model of ragweed pollen extract (RWE)-induced allergic asthma treatment with fidarestat prevented the expression of IL-13, phosphorylation of STAT-6 and transformation of epithelial cells to goblet cells in the lung. Additionally, while the AR-null mice were resistant, wild-type mice showed goblet cell metaplasia after challenge with RWE.

CONCLUSIONS

The results show that exposure of SAEC to IL-13 caused goblet cell metaplasia, which was significantly prevented by AR inhibition. Administration of fidarestat to mice prevented RWE-induced goblet cell metaplasia and AR null mice were largely resistant to allergen induced changes in the lung. Thus our results indicate that AR inhibitors such as fidarestat could be developed as therapeutic agents to prevent goblet cell metaplasia in asthma and related pathologies.

Mechanism of asthmatic exacerbation by ambient air pollution particles

In the previous two to three decades, the prevalence of asthma has risen in numerous countries of the world. Correlating with this elevated prevalence of asthma, societies have observed increased air pollution from specific sources. Studies have implicated certain pollutants in asthmatic exacerbation. Particulate matter (PM) is the pollutant most frequently identified with worsening of this airway disease. PM is a temporally and spatially shifting suspension of solids and liquids originating from both natural and anthropogenic sources. Exposures to elevated levels of PM have been associated with asthmatic exacerbations by employing a diverse array of end points, including respiratory symptoms, use of medication, medical visits, emergency room visits, hospital admissions and pulmonary function decrements. Pertinent to worsening of asthma by ambient air PM, there are other particle-associated exposures that similarly precipitate asthmatic exacerbations. These include traffic-associated pollutants, diesel exhaust, emissions from gas and wood stoves, burning of biomass and environmental tobacco smoke. It is widely accepted that the biological effects exerted by all particle exposures result from oxidative stress. This stimulates cell signaling, transcription factor activation and mediator release in the respiratory tract, culminating in inflammation. Other postulated mechanisms for asthmatic exacerbation following PM exposure include an impact on the incidence of infections and adjuvant effects.

Wound repair and anti-oxidative capacity is regulated by ITGB4 in airway epithelial cells

Integrin beta 4 (ITGB4) is a structural adhesion molecule which engages in maintaining the integrity of airway epithelial cells. Its specific cytomembrane structural feature strongly indicates that ITGB4 may engage in many signaling pathways and physiologic processes. However, in addition to adhesion, the specific biologic significance of ITGB4 in airway epithelial cells is almost unknown. In this article, we investigated the expression and functional properties of ITGB4 in airway epithelial cells in vivo and in vitro. Human bronchial epithelial cell line (16HBE14O-cells) and primary rat tracheal epithelial cells (RTE cells) were used to determine ITGB4 expression under ozone tress or mechanical damage, respectively. An ovalbumin (OVA)-challenged asthma model was used to investigate ITGB4 expression after antigen exposure in vivo. In addition, an ITGB4 overexpression vector and ITGB4 silence virus vector were constructed and transfected into RTE cells. Then, wound repair ability and anti-oxidation capacity was evaluated. Our results demonstrated that, on the edge of mechanically wounded cell areas, ITGB4 expression was increased after mechanical injury. After ozone stress, upregulation expression of ITGB4 was also detected. In the OVA-challenged asthma model, ITGB4 expression was decreased on airway epithelial cells accompanying with structural disruption and damage of anti-oxidation capacity. Besides, our study revealed that upregulation of ITGB4 promotes wound repair ability and anti-oxidative ability, while such abilities were blocked when ITGB4 was silenced. Taken together, these results showed that ITGB4 was a new interesting molecule involved in the regulation of wound repair and anti-oxidation processes for airway epithelial cells.

Aldose reductase inhibition suppresses the expression of Th2 cytokines and airway inflammation in ovalbumin-induced asthma in mice

Airway inflammation induced by reactive oxygen species-mediated activation of redox-sensitive transcription factors is the hallmark of asthma, a prevalent chronic respiratory disease. In various cellular and animal models, we have recently demonstrated that, in response to multiple stimuli, aldose reductase (AR) regulates the inflammatory signals mediated by NF-kappaB. Because NF-kappaB-mediated inflammation is a major characteristic of asthma pathogenesis, we have investigated the effect of AR inhibition on NF-kappaB and various inflammatory markers in cellular and animal models of asthma using primary human small airway epithelial cells and OVA-sensitized/challenged C57BL/6 mice, respectively. We observed that pharmacological inhibition or genetic ablation of AR by small interfering RNA prevented TNF-alpha- as well as LPS-induced apoptosis; reactive oxygen species generation; synthesis of inflammatory markers IL-6, IL-8, and PGE(2); and activation of NF-kappaB and AP-1 in small airway epithelial cells. In OVA-challenged mice, we observed that administration of an AR inhibitor markedly reduced airway hyperresponsiveness, IgE levels, eisonophils infiltration, and release of Th2 type cytokines in the airway. Our results indicate that AR inhibitors may offer a novel therapeutic approach to treat inflammatory airway diseases such as asthma.

Tobacco smoking, fruit and vegetable intake modify association between -21A>T polymorphism of catalase gene and risk of bronchial asthma

Although oxidative stress is a cardinal feature of bronchial asthma, the role of interactions between environmental oxidant/antioxidant exposures and antioxidant genes in asthma aetiology has yet to be determined. The present study was conducted to investigate whether two common polymorphisms -21A > T and -262C > T of catalase (CAT) gene are associated with susceptibility to asthma in a Russian population and to test the hypothesis that the asthma risk attributed to CAT genotypes could be dependent on both oxidant (tobacco smoking) and antioxidant (fruit and vegetable intake) exposures. A total of 429 unrelated Russian individuals from Central Russia were recruited in the study, including 215 asthmatics and 214 sex- and age-matched healthy controls. Genotyping analysis for the CAT gene polymorphisms was performed by PCR-RFLP assays. The frequencies of both allele -21A (OR 0.73 95%CI 0.55-0.96 p = 0.03) and -21AA CAT genotype (OR 0.42 95%CI 0.23-0.76 p = 0.004) were higher among asthmatics than among healthy controls. The frequency of -21AA genotype of the CAT gene was significantly higher in patients with allergic (OR 0.47 95%CI 0.25-0.92 p = 0.024) and nonallergic (OR 0.32 95%CI 0.14-0.71 p = 0.004) asthma in comparison with controls (at the Bonferroni corrected p value less than 0.025). Polymorphisms -21A > T and -262C > T of the catalase gene were in a positive linkage disequilibrium (p < 0.0001). Smokers who carried -21AA genotype had an increased risk of nonallergic asthma (p = 0.002), whereas nonsmoker carriers of this genotype did not have the risk of any variant of the disease. Notably, no association of CAT genotype -21AA with asthma was found in high fruit and vegetable consumers, whereas low fruit and vegetable consumers (one time per day or less often) possessing this genotype were at increased risk of both allergic (p = 0.013) and nonallergic (p = 0.008) asthma. This is the first study reporting an association of polymorphism -21A > T of the catalase gene with allergic and nonallergic asthma. We also found, for the first time, that cigarette smoking and fruit and vegetable intakes have potentially inverse modifying influences on the asthma risk in individuals with -21AA CAT genotype and that the gene-environment interactions that were found support the biologic plausibility of catalase gene for the development of bronchial asthma.

A review of candidate pathways underlying the association between asthma and major depressive disorder

OBJECTIVE

To consider the mechanisms that may link asthma and major depressive disorder (MDD). Asthma and MDD co-occur at higher rates than expected, but whether this reflects shared underlying pathophysiological mechanisms is not known.

METHODS

A review of the epidemiological data linking asthma and MDD was conducted and the possible biological mechanisms that could account for the high rate of this comorbidity were reviewed.

RESULTS

MDD occurs in almost half of patients with asthma assessed in tertiary care centers. Dysregulation of the hypothalamic pituitary adrenal axis may predispose people to both MDD and asthma, and similar alterations in the immune, autonomic nervous, and other key systems are apparent and may contribute to this increased risk of co-occurrence.

CONCLUSIONS

High rates of MDD in asthma may result from the stress of chronic illness, the medications used to treat it, or a combination of the two. The high level of co-occurrence may also reflect dysregulation of certain stress-sensitive biological processes that contribute to the pathophysiology of both conditions.

Nitric oxide-mediated activation of NADPH oxidase by salbutamol during acute asthma in children

A wide variety of reactive oxygen species (ROS) such as superoxide anion, hydroxyl radical and hydrogen peroxide, and reactive nitrogen species such as nitric oxide (NO) and peroxynitrite are known to be involved in pathophysiology of bronchial asthma. We have investigated, in this study, the status of NADPH oxidase (NOX), a major source of superoxide anion production, in peripheral blood lymphocytes (PBL) from asthmatic patients in relation to salbutamol treatment. PBL isolated from patients with bronchial asthma were found to have a significantly increased activity of NOX. Plasma levels of malondialdehyde (MDA), an index of lipid peroxidation, and NO were also markedly elevated in asthmatic patients compared to control samples. A significantly decreased catalase activity observed in PBL from our patients underscored the severity of oxidative stress during asthma. Treatment of PBL with salbutamol (10 microg ml(-1)), prevented the attenuation of catalase activity but significantly increased the levels of NO and NOX activity. Levels of NOX-1 mRNA were significantly (p < 0.001) increased in PBL following treatment with NO donor (500 microM), S-nitroso-N-acetyl penicillamine (SNAP). Western blot analysis revealed that gp91phox protein was also significantly (twofold-threefold) increased following treatment with SNAP. The observed transcriptional regulation of NOX-1 and gp91phox by NO was observed to result in an increased NOX activity as well. This study concludes that salbutamol treatment enhances superoxide anion production in asthma patients through NO-mediated mechanisms, however it exerts beneficial antioxidant effects through activation of catalase and attenuation of lipid peroxidation.

A case-control study of the relation between plasma selenium and asthma in European populations: a GAL2EN project

BACKGROUND

There is evidence that selenium levels are relatively low in Europe and may be falling. Low levels of selenium or low activity of some of the enzymes dependent on selenium have been associated with asthma.

METHODS

The GA(2)LEN network has organized a multicentre case-control study in Europe to assess the relation of plasma selenium to asthma. The network compared 569 cases in 14 European centres with a diagnosis of asthma and reporting asthma symptoms in the last 12 months with 576 controls from the same centres with no diagnosis of asthma and no asthmatic symptoms in the last 12 months.

RESULTS

All cases and controls were selected from the same population defined by age and place of residence. Mean plasma selenium concentrations among the controls ranged from 116.3 microg/l in Palermo to 67.7 microg/l in Vienna and 56.1 microg/l among the children in Oslo. Random effects meta-analysis of the results from the centres showed no overall association between asthma and plasma selenium [odds ratio (OR)/10 microg/l increase in plasma selenium: 1.04; 95% confidence interval (CI): 0.89-1.21] though there was a significantly protective effect in Lodz (OR: 0.48; 95% CI: 0.29-0.78) and a marginally significant adverse effect in Amsterdam (OR: 1.68; 95% CI: 0.98-2.90) and Ghent (OR: 1.35; 95% CI: 1.03-1.77).

CONCLUSION

This study does not support a role for selenium in protection against asthma, but effect modification and confounding cannot be ruled out.

Influence of age on the development of immunological lung response in intrauterine undernourishment

OBJECTIVE

We investigated the effect of intrauterine undernourishment on some features of asthma using a model of allergic lung inflammation in rats. The effects of age at which the rats were challenged (5 and 9 wk) were also evaluated.

METHODS

Intrauterine undernourished offspring were obtained from dams that were fed 50% of the nourished diet of counterparts and were immunized at 5 and 9 wk of age. They were tested for immunoglobulin E anti-ova titers (by passive cutaneous anaphylaxis), cell count in the bronchoalveolar fluid, leukotriene concentration, airway reactivity, mucus production, and blood corticosterone and leptin concentrations 21 d after immunologic challenge.

RESULTS

Intrauterine undernourishment significantly reduced the antigen-specific immunoglobulin E production, inflammatory cell infiltration into airways, mucus secretion, and production of leukotrienes B(4)/C(4) in the lungs in both age groups compared with respective nourished rats. The increased reactivity to methacholine that follows antigen challenge was not affected by intrauterine undernourishment. Corticosterone levels increased with age in the undernourished rats' offspring, but not in the nourished rats' offspring. Undernourished offspring already presented high levels of corticosterone before inflammatory stimulus and were not modified by antigen challenge. Leptin levels increased with challenge in the nourished rats but not in the undernourished rats and could not be related to corticosterone levels in the undernourished rats.

CONCLUSION

Intrauterine undernourishment has a striking and age-dependent effect on the offspring, reducing lung allergic inflammation.

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.

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.

Lung lining fluid glutathione attenuates IL-13-induced asthma

GGT(enu1) mice, deficient in gamma-glutamyl transferase and unable to metabolize extracellular glutathione, develop intracellular glutathione deficiency and oxidant stress. We used intratracheal IL-13 to induce airway inflammation and asthma in wild-type (WT) and GGT(enu1) mice to determine the effect of altered glutathione metabolism on bronchial asthma. WT and GGT(enu1) mice developed similar degrees of lung inflammation. In contrast, IL-13 induced airway epithelial cell mucous cell hyperplasia, mucin and mucin-related gene expression, epidermal growth factor receptor mRNA, and epidermal growth factor receptor activation along with airway hyperreactivity in WT mice but not in GGT(enu1) mice. Lung lining fluid (extracellular) glutathione was 10-fold greater in GGT(enu1) than in WT lungs, providing increased buffering of inflammation-associated reactive oxygen species. Pharmacologic inhibition of GGT in WT mice produced similar effects, suggesting that the lung lining fluid glutathione protects against epithelial cell induction of asthma. Inhibiting GGT activity in lung lining fluid may represent a novel therapeutic approach for preventing and treating asthma.

Airway smooth muscle relaxation is impaired in mice lacking the p47phox subunit of NAD(P)H oxidase

NAD(P)H oxidase is one of the critical enzymes mediating cellular production of reactive oxygen species and has a central role in airway smooth muscle (ASM) cell proliferation. Since reactive oxygen species also affect ASM contractile response, we hypothesized a regulatory role of NAD(P)H oxidase in ASM contractility. We therefore studied ASM function in wild-type mice (C57BL/6J) and mice deficient in a component (p47phox) of NAD(P)H oxidase. In histological sections of the trachea, we found that the area occupied by ASM was 17% more in p47(phox-/-) than in wild-type mice. After correcting for the difference in ASM content, we found that force generation did not vary between the two genotypes. Similarly, their ASM shortening velocity, maximal power, and sensitivity to acetylcholine, as well as airway responsiveness to methacholine in vivo, were not significantly different. The main finding of this study was a significantly reduced ASM relaxation in p47phox-/- compared with wild-type mice both during the stimulus and after the end of stimulation. The tension relaxation attained at the 20th second of electric field stimulation was, respectively, 17.6 +/- 2.4 and 9.2 +/- 2.3% in null and wild-type mice (P <0.01 by t-test). Similar significant differences were found in the rate of tension relaxation and the time required to reduce tension by one-half. Our data suggest that NAD(P)H oxidase may have a role in the structural arrangement and mechanical properties of the airway tissue. Most importantly, we report the first evidence that the p47phox subunit of NAD(P)H oxidase plays a role in ASM relaxation.

Inhibitory effects of N-acetylcysteine on the functional responses of human eosinophils in vitro

BACKGROUND

Oxidative stress appears to be relevant in the pathogenesis of inflammation in allergic diseases like bronchial asthma. Eosinophils are oxidant-sensitive cells considered as key effectors in allergic inflammation.

OBJECTIVE

The aim of this work was to study the effects of the clinically used antioxidant N-acetyl-L-cysteine (NAC) on the functional responses of human-isolated eosinophils.

METHODS

Human eosinophils were purified from the blood of healthy donors by a magnetic bead separation system. The effects of NAC were investigated on the generation of reactive oxygen species (chemiluminescence and flow cytometry), Ca(2+) signal (fluorimetry), intracellular glutathione (GSH; flow cytometry), p47(phox)-p67(phox) translocation (Western blot) and eosinophil cationic protein (ECP) release (radioimmunoassay).

RESULTS

NAC (0.1-1 mm) inhibited the extracellular generation of oxygen species induced by N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) and eotaxin (in the presence of IL-5) with -logIC(50) values of 3.61+/-0.03 and 3.36+/-0.09, respectively. Also, the intracellular generation of hydrogen peroxide was virtually abolished by NAC (0.5-1 mm). NAC (1 mm) did not alter the fMLP-induced Ca(2+) signal but augmented the eosinophil content of reduced GSH and inhibited p47(phox)-p67(phox) translocation. NAC inhibited the release of ECP ( approximately 90% inhibition at 1 mm) from fMLP-activated eosinophils.

CONCLUSION

Inhibition by NAC of human eosinophil functions in vitro is potentially useful in the treatment of allergic inflammation.

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.

The relationship between polymorphisms in the glutamate cysteine ligase gene and asthma susceptibility

The present study was designed to investigate an association of common -588C/T and -23G/T polymorphisms within glutamate cysteine ligase modifier subunit gene with susceptibility to bronchial asthma. A total of 435 ethnically Russian subjects were recruited in this study, including 221 patients with asthma and 214 sex and age matched healthy subjects. As previously reported, the -588C/T and -23G/T polymorphisms were completely linked. The -588TT/-23TT genotype was found to be associated with decreased risk of allergic asthma after adjustment for age, gender and smoking status using multivariate logistic regression analysis (OR=0.33 95% CI 0.15-0.70, p=0.036). However, the -588CT/-23GT genotype was associated with increased risk of non-allergic asthma (OR=2.03 95% CI 1.05-3.90, p=0.06). This is a first study reporting the association between genetic variations in the glutamate cysteine ligase gene and susceptibility to bronchial asthma.

Studies on logP, retention time and QSAR of 2-substituted phenylnitronyl nitroxides as free radical scavengers

As reported in our previous paper [Y. Wu, L. Bi, W. Bi, Z. Li, M. Zhao, C. Wang, J. Ju, S. Peng, Bioorg. Med. Chem. 14 (2006) 5711-5720.], a series of novel 2-substituted nitronyl nitroxides were synthesized and characterized to show enhanced free radical scavenger properties. Here, the logP values and retention time (alternatively represented as logK) of these 20 compounds were determined by the shake-flask method and HPLC analysis, respectively. We found that the prediction of logP directly from the measured logK value can result in a high accuracy, thus the determination of time-consuming logP can be replaced by the simple HPLC analysis. Using the conventional Hansch method, the QSAR equations of these nitronyl nitroxides were established to predict their capability of trapping free radicals such as *NO, *H(2)O(2) and *OH. Although the overall predictive accuracy is reasonable, it was found that the logP values for the compounds are not significantly related to their capability of trapping free radicals. Moreover, an improved QSAR analysis was performed by choosing new molecular descriptors generated from e-dragon server. The increased predictive accuracy suggests that these new QSAR models have practical application in screening new potential scavengers from the derivatives of 2-substituted phenylnitronyl nitroxides.

Novel 2-substituted nitronyl nitroxides as free radical scavengers: Synthesis, biological evaluation and structure–activity relationship

To develop more potent small molecules with enhanced free radical scavenger properties, we designed and synthesized a series of nitronyl nitroxide derivatives 4a-h. A lead compound 4f was discovered based on Ach-induced vascorelaxation assay. Further chemical modification based on this scaffold provided a new series of 2-substituted phenylnitronyl nitroxide derivatives 6a-s. The newly synthesized compounds 6a-s possess improved radical scavenger's activity based on PC12 cell survival assay. Compounds 6g,n,o, and s are some of the most potent compounds in terms of NO, H(2)O(2), and OH scavenging ability. 2-Substitued phenylnitronyl nitroxides had a higher radical scavenging activity with the electron-donating group (EDG). In contrast, the introduction of electron-withdrawing group (EWG) to the aromatic ring led to a dramatic decrease in its radical scavenging activity. These results suggest that the electron-donating group (EDG) of the aromatic ring may be an important factor influencing the radical scavenging behavior of these compounds, and the potency of free radical scavenging activity largely depended on the position and electronic properties of the phenyl ring substituents. The enhanced radical scavenging capacities of the novel 2-substituted nitronyl nitroxides may be potential drug leads against the deleterious action of ROS (reactive oxygen species)/RNS (reactive nitrogen species).